Instead of getting one item, a list of ten (or so) items appears and you pick one, like an end reward list.
It would still take a while to get the "perfect" item, but you're a lot more likely to get a "pretty good" item. Or something useful enough that the challenges don't seem like a total waste of time.
It would be a lot easier to program than some of the other ideas, so could be used as a temporary measure if the devs wanted to add the "build what you want" ideas later.
Geoff.