I would agree that redesigning my city is a ton of fun. A lot of my "down time" during this game is spent strategizing over a better design, the next big upgrade, a guest race requirement, etc. Then there is the time spent figuring out how many expansions I'd need, how to get them, which culture to bid farewell to...yada yada. But I have to agree with Iyapo that being forced to save up multiple expansions, or puzzle out a way to make it all work is one of my favorite parts of this game. If it became as easy as clicking the "move" button, there would be fewer hard decisions/sacrifices to make...which I think would change the game on a fundamental level. For players like myself, it would be less fun in the end.
THAT said, I wouldn't mind one of those "temporary" expansions you guys are talking about as a one-time-use event prize once in a very blue moon. What a treat it would be to indulge the desire to completely redesign my city just for the fun of it! But as a hard to get reward which expires after you've used it, not a game feature please.