50/50 seems way too much. I don't want them just throwing in any 3rd party character who's ever made an appearance on a Playstation. For a 3rd party to be in, I want them to have to have been exclusive to Playstation at one point, and to have been vital in building Playstation's popularity or identity.
Snake, Cloud, Lara Croft, Crash, and Spyro are the only ones that I think should definitely be in. I'd also be open to Dante from DMC and some more obscure characters like Selvaria from VC. But if we get to the point where characters like Ezio, James Bond (lol), CoD soldier, or whatever are put in, I'll be a little disappointed.