The problem with that is that sony doesn't own those. In order to have recognizable characters, it would have to mainly be a 3rd party fest. They sold off crash and spyro to activision. Sony is known for it's great 3rd party support, not first party. They have a good amount of great first party, but when people think of their favorite games on PS1, PS2 and even PS3, 80% of them will be 3rd party (MGS, Final Fantasy, Crash bandicoot, Spyro, tomb raider, etc). Playstation's 'All stars' don't actually belong to sony.
That and the game's 'final smash only' mechanic was dumb. How bad would smash bros be if you could only KO with final smashes.