Ok, so I got to thinking that there could be something similar to Levequests and beast quest projects, but you work on something much, much larger, like a Palace room, a castle tower, or a Fortress/City Wall. Unlike other housing projects, the test would require High quality versions of some common materials and objects (mortar, walls, etc.) but the finished projects would pay out like x10 to x100 usual leve quests, so like anywhere from 10,000 to 300,000 and/or include rare rewards like level 2-4 materia, moonstones, or possible other useful crafting devices.

The scale of the project would be similar to 10-100 regular quests, but it would give us more to mess around with in regard to housing. Variations to paying in gil might be things like stacks of silver/gold coins.

A special Title and Unique Vending options might also be awarded, including special permissions to construct odd things in the Housing Areas or recipes that normally are just drops or grand company exchanges.