it would be good for RP to change the (mouseover-)text from the potions (permissions based, per user/group) and only show "unknown potion" or something like this maybe its possible to do this with spout, dunno and i think it has to do with packet filtering, where i have no clue from since potions are only in the next release, any other item would do the same spout has this feature on the loooong todo list at most bottom, they said that they will only implement it if someone will make a pull-request
ok, maybe this can be used more generaly ... remove/replace text from any items per player (a simple list would be ok)
I don't know exactly how potions work but they got a certain data value, a number which gives the special effect. My Idea is that when you craft a potion, that number will be the outcome +13, so the potion will actually carry the wrong information. When the user drinks the potion, the data value will be -13, and the potion will be correct, and effects will be applied Also when you place a potion in a brewing stand, it will -13 and get the right data value again.
AFAIK, item tooltips are set in the en_US.lang file in the client's minecraft.jar file, so not really possible in bukkit. Not sure about spout though...
spout has already a renaming api for items, but it's only global and not player spezific. but it is possible.