As for current housing wards, make them all personal instead. But increase their wards up to 100~200+ to make sure that even one player who owns 8 alts could purchase it if they want to, so that people won't have to complain ever about plots being short or limited. Every time whenever Wards are being full in any server or even sizes are full, the server should recognize it and build a new ward automatically. Whether if it is large/medium. Not everyone is willing to stay small forever.
When player relinquish the land, please give 80-90% portion of the land as resale. To prevent the people from over price selling the land and to avoid violation of Term of Service.
Lastly, if people who are personal wishes to join in FC ward that are not FC members and purchase in the plot - perhaps they can get special permission to build housing in there. Now should these people who are in FC ward wish to leave FC or had special access wishes to move out, they'd be moving to personal ward where it's strictly for non-FC players only to purchase in these wards. They can transfer for free and grab the plots that are available within those 50-200 wards, whether it'd be small,medium or large.