This discussion may contain spoilers!
Okay, before s2e4, it was almost unanimous that Clem should be the playable character forever and always. Then, Amid the Ruins disappointed many players. (Personally, I've liked the whole of season 2, but that's beside the point). And I saw a dramatic increase in players wanting to "play from a different perspective than Clem." I think what's really going on is that you think a new playable character would allow Telltale to make new seasons better, or at least keep them from soiling Clem further by involving her in more bad seasons. If that's you, I have some points to make. (If you really just want to play from a different perspective, I dunno what to tell you. I'm not even sure what you mean by a different perspective. You mean, just, taller?)
Let me start with the damage it could do to remove Clem as PC in Season 3:
1) Big Picture Enjoyment of the Walking Dead Game series:
I'm looking at the big picture of the game, and I'm seeing the epic story of a young person whose greatest influence was a once-murderer who died for her in the ZA. You have to admit, at least so far, that's what the series is. Is STARTING out as. Season 2 is almost over, but if you ask me, the series is just getting warmed up. It has to be. A story like "a young person whose greatest influence was a once-murder" simply cannot end where Season 2 is going to end.
S2e5 simply cannot possibly have a satisfying end to that story. First off, there hasn't been any build up to an end epic enough. Lee's story was satisfying because, in the end, it made sense. Yes, it was shocking that Lee died, but that event actually did have build up to it. We spent all of season 1 building a love between Lee and Clementine that Lee would die for. And then he did. He died for it.
Most people say they'd want Clem to live but as the sidekick she was in Season 1 (which is another reason I think people just want a new PC because they think a return to the old formula would mean a return to the old quality). But whether Telltale ended her story by killing her or not, the story of a young person whose greatest influence was a once-murderer would be over. And there hasn't been any build up to the end of that story.
If there's been build up to anything, it's that Clem can't trust anyone in the ZA. The writers even said at one point that, in Season 2, instead of Lee figuring out who to help, we have Clementine figuring out who to trust to take care of her. From what I've seen so far, the answer to who she can trust is NO ONE. I mean, I like Kenny a lot, but I don't trust him to take care of Clem consistently. And that's the key term: consistent. Has anyone this season been the CONSISTENT protective presence for Clem? I don't think so.
So if they ended Clem's story now, the overview of the series would be something like "Wow, what a horribly sad, wonderfully inspiring tale of Lee Everett going from murderer to martyr in protecting smart, little Clementine. How exciting! Now, we get to play as Clementine and deal with losing Lee and growing up in the ZA. Oh, wait, one season with a moral about how you can't trust anyone and hardly a mention of Lee. No more Clem. Okay. Kind of a letdown."
So, while a new PC might appease players who were disappointed in s2e4, it would detract from the big-picture enjoyability of the series.
2) Clementine's Character Arc
Telltale is in fact not just writing a game where we get to run around making dark choices. I think it's apparent from Season 1 that they have an actual story in mind, with actual character arcs and actual themes to play out.
One of the things that made Lee's story so great is that he had such a great character arc. No matter what happened in the middle, Lee went from being a murder to a savior. We first see Lee in the back of a police car on his way to prison. I mean, he must have thought his life was over. He'd live a long, dull life in prison regretting what he'd done, and he'd die alone in a cell. It seemed there was no hope. But it turned out, no. He lived a short, exciting life teaching and protecting an orphan girl, and he died for someone he loved. There was hope. He loved Clementine. He was redeemed. Lee's story has a definite trio of inspiring themes: hope, love, and redemption.
What are the themes in Clementine's story? What's her arc?
So far the themes are trust, or lack thereof, and perhaps survival. And her arc appears to be going from a young girl who trusts to one who doesn't. There's nothing inspiring about any of that. It's all really anticlimactic and depressing. And that's why Clem's story has to go on. It has to be as meaningful as Lee's was. As sad as Lee's death was, it was also beautiful. Clem's end should also be beautiful. Don't you think?
Telltale could end Clem's story exactly how they ended Lee's and have her die the ultimate heroic death, and that could work quite well. But not in s2e5. For example, Clem could die for Rebecca's baby, and that would be very heroic, but it wouldn't be satisfying because there hasn't been any build up to it. Clem has no relationship with Rebecca's baby. If she died for it, it would mean Clem is a good person, but that's all it would mean. Lee's death was so amazing because it had so many layers of meaning. Hope, love, redemption, as I said before.
If, on the other hand, Telltale ended Clem's story by just changing PCs...Maybe it's just me, but I feel like that would be even more unsatisfying, because it robs Clementine of that ultimate heroic death. It wouldn't even mean she was a good person. It would just mean she's not the PC anymore.
At this point, there's no way Clementine's character arc could seem inspiring or satisfying by the end of Season 2.
3) New Character Attachability
Telltale used some pretty amazingly intricate tricks to get us as attached to Lee and Clementine.
I mean, it helps that, for a good long while, Telltale kept it completely uncertain whether Lee actually did commit a crime. The first line in the game is, "Well, I guess you didn't do it then." I, personally, was convinced he didn't do it, whatever "it" was. So I had nothing against him when he found Clementine and took her under his wing without a second thought. His selflessness there got him major points with me.
So, by the time we find out he did do it, we're already in love with him for being so selfless, not just to Clementine, but also to Shawn/Duck/Lilly/Larry/anyone else he'd been kind to at that point. And at the same time we find out he did do it, we find out why he did it. And it was a sympathetic motive. He killed the guy who was cheating with his wife. That doesn't make it okay, but it makes it relatable. Lee was both flawed and sympathetic. Perfect combo!
All this within the first half of episode one. And boom, you're attached to Lee.
You become attached to Clementine because she's so smart and innocent and kind and protect-able (there are numerous examples I am too lazy to write). However, you're also attached to her because of her powerful connection to Lee. Not to mention, she has time on her side. All of season 1 and 2 get you attached to Clem.
Now. If Telltale were to introduce a new PC, or even use an existing character, they'd have to come up with even more pretty amazingly intricate tricks to get us attached to them. I'm not very attached to any of the present characters, besides Clem. So at least, for people like me (who Telltale doesn't want to lose), these tricks would be essential to get us to play the game. And tricks like those take some serious thinkerbox power.
So basically, I'm not saying they should keep Clementine as PC because no one else could possibly be PC. I'm saying they should keep Clementine as PC because her story isn't complete/meaningful yet. And Telltale could use all available thinkerbox power to get us attached to a new PC. Or they could use all available thinkerbox power to complete Clementine's story and make it just as meaningful as Lee's. Seems like an easy choice to me.
Now, let's talk about all the great ways Clem's story could continue if she remains PC:
1) Dealing with Lee's Death
I'd like to see Clem deal with Lee's death. I suppose she did deal with it in some way in the last two years, but I want to SEE it. And although two years were skipped to make Clem older, bigger, wiser, more capable, etc., we still have the opportunity to see her deal with Lee's death. She may have already dealt with losing her best friend, but did she deal with losing the final person on Earth she'll ever be able to trust? If Season 2 goes like I think it will, she'll end up feeling betrayed by everyone in her current group. And this could lead to her thinking more and more about Lee. I hope so.
2) Finding Her Purpose in the ZA
Clem looks like she's going to live a good long while, zombie apocalypse or no. At some point, she's got to become bored with just surviving. She'll want a purpose. I like to think she'd want to be a teacher because that's what Lee was. But she'd have to work out how to be a teacher in the ZA. I can see the seasons going: Season 2 - Trust, Season 3 - Guilt, Season 4 - Purpose, Season 5 - Heroism/Love/Sacrifice. And there's endless possibilities in between. Maybe Clem would go dark/selfish before going light/heroic. That would be interesting.
3) Clem Becoming a Hero
I'd like to think, eventually, she'll follow more and more solidly in Lee's footsteps. Believe it or not, characters can have solid patterns of behavior and still be the PC. The writers are not supposed to give you the option of all possible actions, but the option for any action the character in question would take.
For example, when Lee crashed and shot the police officer, he saw Clem and called out for help. When my mom played that part, she didn't want to call out for help. She wanted to take the opportunity to have Lee flee custody, and she was frustrated that wasn't an option. But of course it wasn't an option. Lee wouldn't have done that.
For an example involving Clem, when Carver orders Carlos to hit Sarah, I chose to say, "It was my fault!" But you'll notice, there is no option to say, "Yes, do it. She's annoying." Because Clem wouldn't have said that. It would have been out of character. But at the same time, I wanted to tell Carver to hit me instead of Sarah, but there was no option to say that. So obviously, Clem isn't a full-blown hero yet, which is fine. Especially since I'd like to see her journey toward becoming that full-blown hero. I want a scene in a future season where something similar happens and Clem offers to take the hit for someone else.
So, those are my arguments for keeping Clem as PC. I'll edit and add as I see fit.
TL;DR: Clem needs to remain PC until her story, character arc, and themes are as complete and inspiring as Lee's were.