We are already far past the point of having instance housing, but who knows. Personally instance housing is better and I think Wildstar and ESO are good examples to take inspiration from.

If I do recall correctly and I could be wrong, they made it into ward so that everyone can convene around the ward square and hang out. The thing is though that you can still do the same with instanced housing, you can setup events in your own house and whatnot and invite people and with party finder people can advertise your event there as well.

Not just that but FC housing has more benefits as they will have their own workshop and FC rooms. Obviously this can be easily resolved if there is another door (Which there is) in the GC area, which leads into a something similar to an apartment but for an FC that leads into rooms and workshops.

As for addressing the Multi-buying option, it'll be really difficult cause there are some people who will buy more than 1 account and will try to buy the entire ward. Instance housing is the only way to prevent this sort of abuse but instance housing is unlikely to be done in FFXIV. Only thing they can do now is just adding more ward, which only extends the problem rather than solving the problem.