Can't have more than one buff naturally but should work together with medicated, FC actions and food buffs(for the most part):
Increase HP/MP/TP regen buffs for 30 min.(hey I can dream)
All the other buffs that can be added as actions by the FC(spritibond, extra seals, etc...).
Increase any of the stats for 30 min - similar way as food but only for a single stat - i.e. observing a vase of beautiful flowers should invigorate your mind, observing the map of eorzea humbles you from it's size thus increasing your piety and such like - should be some reason why something gives you a buff.
If you eat food at the table it should double the duration of it - you sat down and had a proper meal not a snack - or double the stat buff.

Prob more ideas there but still that's a start.