Bigger apartment sizes and housing related side activities moved elsewhere in the game. If someone wants to solo build and airships/subs alone let them with a workshop accessible by your Grand Company in a new rank. If someone just wants to crossbred some plants I see no reason the Island Sanctuary can't have a garden plot to allow access to that. Apartments having bigger sizes would also be a great gil sink for the game if they are prices closer to actual housing, albeit at a slightly cheaper amount.