You can move from one room type to another or from one resort to another in the middle of the trip. There will be separate reservation numbers and confirmations for each room, so I guess that's not technically the same "booking". And while it may be a pain to move there are a couple of incidental benefits: if you stayed in 1 room for 7 days, you get just a towel and trash visit on the 4th day, but if you move, you get the fresh linens and towels and clean room when you switch. You can sign up for the dining plan for just one of the rooms rather than for the whole trip. The bellhops can take and store the luggage when you check out of the first room and then bring them to the new room when you check back in. However, you will need to check out of the first room by 11 and there's no guarantee that the new room will be ready until after 4 pm, so you really won't be able to count on using the room during the day of your move.
Hope that helps.