I wish there was an option to transfer an FC house into a private one, without losing all the decorations. My husband and I own a FC house on our alts and wish we could set our mains as Tenants to it.

Ideas to serve as solutions to the problem

Allow an FC to transfer house ownership to a single person, thereby making the home private. (This would of course, remove workshops) You could make it so you could only transfer if no private rooms were present.
Allow FC houses to designate people to be tenants, even if the people are not in the same FC.
Allow FC Alliances, making it so people can have access to multiple FC homes.