Hello,
I hope that ffxiv will be implementing exp chains, on that note I would like to see parties get exp chain buffs when a certain chain has been reached.

For example, if a party reaches exp chain #5 all disciplines of war will receive TP regen and all disciplines of magic will receive MP regen. When the chain breaks the buff is lost.

Other buffs could be increased acc/macc/atk/ etc.

Of course SE would have to test for game balance, but I think it would be a cool reward for the efficiency of a party.