This is better for short-sleeve shirts (tees, tanks, polos, et.) but, it can be used with button shirts. You would just leave the shirt buttoned all the time. Every once in a while, you could iron that little hem near the buttons that always seems to want to fold over.
Yes, you do want the shirts taut, so naturally, different forms are made to fit different sizes. An adjustable one is always a possibility.
By the way, how much did you pay for your magic hamper?
Those are some great suggestions. I wouldn't know how feasible some of it would be. But it's worth considering. I can picture a flexible form that actually molds to the exact shape of the shirt (kinda like a sunshade for your windshield).
Anyway, thanks for the feedback, guys. That's what it's all about.