Okay, here's a proposal I've just came up with, a kind of compromise. How about we do a Walking Dead relaunch as suggested, and everyone needs to pick someone from our core cast until its filled, but then let people who are playing as one of that cast pick up a second character that is NOT part of the group, be it a comic character off doing something elsewhere or their own created character who could later join the group.
This way we can maintain the elements of this current RPG I'm getting the idea that people like from this discussion - such as getting to play their own characters and do their own thing - while at the same time addressing its weaknesses by introducing this new, more structured Walking Dead set-up.
Another idea I've had, which also allows for original characters and not being tied down to working within a limited choice of characters in a restricted group: I call it the "guest star" strategy. It ties into a more GM-directed game. Allow me to explain it a bit. You have an RPer who is interested in the game, but doesn't watch The Walking Dead, or isn't interested in a long-term commitment. They can PM one of the GMS, and say they'd like a "guest star" role. Then, the GM plans out with them a short-term role they can play on one of the survivors' pit-stops, something equivalent to what Dr. Jenner was in the season finale.
For example, we could do a storyline where an RPer "guest star" is introduced as a nice man who owns a big farmhouse and offers the survivors shelter, but who turns out to be an axe-murdering cannibal looking for fresh meat. Then the group kill him and move on, the RPers short term gig wraps.