Ps2 Limitations aside.
one concept id love to see is 3+ bedroom mog houses.

1 room with a balcony view * chosen by a quest *

you would have door ways that would allow you to walk through all 3 rooms , each additional room would be a quest / gil requirement *think manny quest but carpenters guild in sandoria*

i know there are quite a few people who have spent millions decorating there mog houses.

Id love to have a Main "Room" , a Blacksmith Store *stall all gp items a manny as a fake npc etc*. And Finally a room with all the Flages and lined by Mannys wearing the Gear Sets ive earned over the years as kinda a path to the balcony.