I reiterate my statement to say NO to customizing existing castles in any way, we would loose the historical design of a castle. I'd much prefer the DEV team to design some new models (6 or so), with new walls, new inside layouts, etc. etc. and allow folks to place these new designs. If you want a new design, then you should either uproot your castle and replace it with a new design ~OR~ allow a design change from inside the housing menu. I prefer forcing folks to make that hard design to uproot, because that would ensure at least some castles will remain in the old design.