Okay, so big pop worlds are having a shortage, and if 3.0 draws in more subs, I can see lower pop servers starting to feel cramped in this area, so I have a few suggestions to hopefully help a bit with the housing shortage (yes, I know, server limitations, but hopefully they'll be able to do it on working servers considering the success of the relaunch):
First, to prevent ghost towns from being created, houses that have seen zero activity of its owners (no sub payment from any personal or FC members) for more than 1 year can be repossessed.
This gives the owner a ticket with which, if they return they can put it back down on any same-size available plot (if the plot is worth less than what the owner originally paid, they get the difference back, if worth more, they are given it in exchange for 50,000 relevant Grand Company seals [Twin Adders in Lavender Beds, Immortal Flames in the Goblet, Maelstrom in Mist]).
If no plot is available, they might unfortunately have to wait or cash in the ticket for the original amount of gil. Furnishings will be stored in a chest by the relevant GC's HQ, so that they can be used for other things if the owner wants to without cluttering up inventory.
Second, instanced apartments in Revenant's Toll. These should be affordable (1mil for a small apartment, 5 mil for a medium and 10 mil for a large, possibly with GC seal requirements, such as 25,000 - 50,000 seals from each GC, lore-reason being to drum up support for Mor Dhona in the rest of the world or something). These should allow limited gardening in flower pots.
Third, instanced apartments in the major cities. Once you've advanced enough in a GC and has paid a enough of relevant GC seals (TA for Grid, IF for Ul, Ms for Limsa) and gil, plus completing a small quest, you can have an instanced apartment in the city, which functions the same as the previous one.
Fourth, let us use the chocobo stables around the world.
Fifth, flying archipelagos and islands. Okay, so the archipelagos would function as the existing wards, where there are different sized flying islands in a neighborhood where you can buy one and build a house. The islands would just be the single, instanced version of that. These are more expensive than apartments and allow more gardening+everything else housing. All come in several sizes/versions as well (some with more plants, some with more crystals, some with more water and so on). This is just a suggestion based on the sky-theme of Heavensward and the flying continents.
Sixth, if a water theme happens, do the same with regular archipelagos and islands. Also, doing underwater housing in instanced "island bubbles" would be cool.