Honestly I'd be happy if they just let us have apartments that use the interior space for medium and small homes; and or access to a new 'garden' interior space and a workshop. Personally I think that's a fair way to test interest in viability for an instanced housing area. Of course upgrading to a larger apartment size should come with a SIGNIFICANT gil sink - as should unlocking extra features like a small gardening terrace or small workshop. However I don't think you'd find too many people that upset with having to save a million or two more gil for the extra space and amenities.