What I'm suggesting is something to the same effect as what the GM layer already does. I would like tokens to show up for some players and not others. Whether it is additional custom layers, or just an advanced token setting. This is similar to what dynamic lighting already does if a Human player has no dark vision and cannot see the obvious pit right before him, while his Elvish friend with darkvision can see the pit while in complete darkness. However, what if I have a trap that one player discovers during combat, and the others don't? Or what if a npc has a high stealth check that keeps him hidden from all players but one? I find that revealing tokens to players who discover it allows them to have a say on how things go, instead of everyone now knowing exactly where something is when only one person discovers it. A really well hidden trap shouldn't be discovered by the entire party even if one person mentions where it is from a distance. This also provides unique options for some more advanced games. Say a pvp situation in an arena. If someone places a trap on the ground you could leave a token behind that they now see and the other players don't.
