The one thing I'd want to be careful about is that I don't wish to remove all the challenge from these sort of traps.
I'd only want to put the nopush zones on platforms where they're _very_ small and prone to griefing. The best example is mario, where the platforms are thinner than a player's bounding box.
If the platform is larger than a player, it's safe to assume that players should be able to handle jumping onto it if another player is present.