This is a great idea. I've been thinking that SQE should be making FFXIV content more replayable, and nothing works better than a cosmetic reward structure. I personally think it'd be really cool if clearing a current expansion ultimate, with players who had not completed it yet, rewarded you with a chocobo feather that allows you to take up more bids on a slot for a house--like consuming a feather gives you 5 extra bids. Obviously would need an extra use for them too, since once you get a house, you won't need them anymore. This would make ultimates more active, too. Maybe for legacy ultimates, you could get 1 extra bid.