I read the question as how would you do housing from the start vs adjusting current housing, so I'd probably do everything instanced. There would be different plot styles/layouts for FCs (FC Keeps) and for personal homes. Various terrain/skybox options with a decent sized area, but probably more of a larger than mansion sized editable area for the player with something similar to WoW/Wildstar where you could plug in different things to other areas of the landscape (Barn, Garden Patch, Workshop, Squadron station, etc) which can be adjusted as needed as there wouldn't be need to worry about the lot side limitations from other houses. Allow the house to be placed anywhere in the editable portion and there would be a much larger outdoor item limit (no other houses' stuff to load up). There'd be an airship dock too for personal airships as well as something bigger in the fc keep area for fc ships. Gardens would be account locked (house sharable or you can get more for alts), but you can upgrade the harvest area a few times. Fixtures like wallpaper and such would be 'learned' and bound to your account. Not sure if I'd make it owner-only for using the decor (restriction null for fcs, but fixtures return to defaults if the person that placed it leaves) or active tenants too. Much more tenants allowed. Seasonal items would come back with each event, but be available year round from the mogstation so if you don't want to wait you can grab it for cash, but if you're strapped for cash you can still wait for the next round to get a chance at items. Alternatively go for the available-one-holiday thing we have now, restrict placement to active members/tenants (items/fixtures removed if person leaves fc/no longer a tenant) and make the items unlocked for the account.
Marketing / management would then dig their claws in and maybe an ounce of that would make it to live without being cash shop biased or scrapped due to whatever they've done with the servers.