This would work ONLY if two other things happen. One, you can store rockets and subassemblies for later, and two, that running a space center takes money. You pay mission control, astronaut trainers, etc. for a reason, you know. That way it would be impossible to exploit the system by building infinite rockets forever, and at the same time have your rockets on-call. Obviously build times would be scaled down to account for it. At most on the order of a week for Whackjovian creations.