My biggest thing would be to put the XX on a diet, like Boost said, loosing 50 lbs would be great. I guess better shocks would be a benefit to alot of riders also, I would still prefer the cheapest shock out there, figure I am going to replace them anyway, the cheaper the stock shocks the cheaper the price of the quad overall. A redesign of the rear suspension to use 10" wheels would also be a good change.
A redesign of the plastics would be nice. After tearing my 700XX down months ago and now getting it back together, I am trying to remember what bolt is used to hold what panel on, I decided this thing is a pain to remove/install the plastics on compared to my 450R's/250R! Needs to be simpler.
Thats really about it, quad isn't anywhere near the best in stock form, but even if it was better, I would probably end up replacing a good amount of stuff anyway, so the cheaper the cost of the quad, the better.
Doug