You are going to spend 20k for your old 150 that will be tbo'd and need another 10k after you burn up the engine. You will technically be allowed to log the time because you had the intent to fly it. IF you are turned in by anybody you are screwed. If you are caught pencil whipping which i guess if you do it that way its a grey area you are screwed. Or you could pay your dues like everybody else to achieve your goals instead of trying to cheat the system. Don't ask "hypothetical" questions. If you didn't consider it you wouldn't have asked.