It's obviously not impossible, but it sounds very resouce-intensive. Not just development resources, but server capacity too. One of the reasons the housing situation is so abysmal is due to the server strain all these custom plots exert. They'd probably have to make some major (and costly) infrastructure upgrades to even try something like this.

I won't say there wouldn't be some creative designs, but with a platform like XIV I don't know that players could actually produce meaningfully different or interesting content.