There's been no real info on moving atm, but they said they were looking into implementing something for moving houses after 3.4 (estimated using patch release averages as being after september). So until then you can obliterate the fc house, have some furniture/all rooms/all airships destroyed and have everyone pay another 300k per room at the new house. Another option is to make a 2nd FC, rank it up to 6 before the patch and buy the large house with that FC, then gradually let people switch over. This still requires them to pay another 300k to switch over and destroys furniture that can't be removed, but it gives them time.