Here's some stuff I'd love to have in MSFS2K2 or whatever:
1)Working radar in the fighter jets so when ATC tells you of other aircraft in the vicinity, you could pinpoint and intercept them!
2) I'm sure my fellow "Open Cockpit" fans would love this one: A fan for the top of your monitor that is controled by the sim so the faster your plane goes, the more "wind" you get in your face.
3)Skydiving planes with the ability to have simulated people jumping from them