I actually had enough Gil for a small plot...

[Niwashi]

And put a minimum level requirement of 50 to buy them, and a quest chain involved, so people can't just infinitely spawn alts to get around that cap.

That's nearly in place already, except the level requirement is 47 rather than 50. Purchasing a house requires being a second lieutenant in your Grand Company, and unlocking that promotion requires a level 47 quest (as well as a few previous quests and several dungeons to complete the GC hunting logs and whichever content you use to earn all the GC seals needed).