Suggestion: Free Company Island
I kind of took this idea from personal islands in FFXI, but I think this could help with some of the housing crisis. This could also apply to personal use, but I'm posting in regard to FCs.
Through some means with the Grand Companies, have it so an unexplored chain of islands has been discovered. After certain requirements are met, the player is allowed to explore and settle on those islands.
Upon embarking to visit the island, the player enters an instanced area; an actual island in the ocean. There could be different designs based on where the island is located, as well as a choice of layouts. This area can be visited by all in the FC, or if used for personal housing, anyone you share the island with. It could also be opened to allow visitors to come to it.
On the island, the players will have an assortment of activities to engage in.
1. Building a house. Upon the island would be an area to craft a house. Kind of like how the workshop functions, where the FC can gather materials and craft the house size of their choosing.
2. Fishing. A fresh water pond could be on the island, as well as salt water fishing along the island. The fish could be unique to the island, and used in unique recipes.
3. Gardening. A larger garden could be placed on the island to give plenty of room for growing crops.
4. Gathering. Like fishing, items found at nodes could be unique to the island, and open up unique recipes.
5. Monster rearing. The player(s) could raise monsters, and use them for items.
6. Scavenging. Finding items washed up on the shores, or randomly around the island.
7. Swimming.
8. Workshops open to more players.
I think this would be a fun addition to the game, and open up more opportunities for players to get involved in housing. Again, it could be utilized for personal use as well.