Really good idea man. It would be awesome to see updated versions of the old characters
But I think it should be unlockable or something u earn
It could be unlocked by getting 100% in single player or there could be references to them on the map and you must take a picture of it to unlock the chracter
That would be nice.
It would be cool to play as old favorites like Tommy, Niko or even Catalina . But I hope they wouldn't lock such a feature to DLC. It would be better if you actually earned it by playing the game, rather than having to purchase DLC for it like with RDR.
Also the GTA 1 and 2 characters don't really have models. Would be weird to play as them.