Player housing would also pave the way for player-made villages, and maybe give crafters an outlet to set up a retainer in their own shop (oh wait... the AH eliminates the purpose for this).

Maybe players can build and set up barricades (i.e., build their own castles) to stop beastman and Garlean empire encroaching onto their land. This gives meaning to the world and adds dynamic siege combat, with players trying to protect what they've built.