Honestly, it's pretty simple: The Private Room should just go with you. If you leave a FC or get kicked from one, your room is still there, just inaccessible until you join a new FC with a company house. Perhaps you have to pay like a 30k 'relocation' fee or something (because SE seems to be bound and determined to make everything cost money), but otherwise the room is just how you left it.
SE's lead developers and designers seem absolutely determined to make things as pointlessly complicated and difficult as they possibly can. Look at Glamour, as a perfect example: Pointlessly complicated and difficult, with very little overall functionality (If I want to have multiple functional outfits, I have to have multiple sets of the same gear glamoured to different things? OH WAIT, you mean the best gear in the game is unique and I can only have one set?).