First, you have to think about your graphics. You are going to need a lot of them if you are going to be switching perspective. You will also need to be a great artist if you are going to draw your object "in-perspective."
Also think how cool it would be if you could actually see the camera switch between perspective. It might be to confusing to just switch top-down to-side in an instant. I might not be explaining myself well.
Please let me know if I make any sense, and I will try to explain better.
Cheers,
Steve