I'd make Noble into an outside SF and Yi into a SG. Train their outside skills until they are where you want them to be, then train both of them some inside skills. Once Noble is capped or so expensive that further training hurts your finances, switch back to guard training and finish off Yi.
I agree with most of this, but I think it's a waste of time to train Yi in inside skills. His IS (not to mention RB & ID) is just too low to make it worthwhile IMO, mostly because you'll have to play him at C on offense, and atrocious IS can't be hidden at another position like atrocious ID can. The problem with not training him is that he has more potential than Noble, and it might take quite a bit of convincing to have Yi just sitting on the sidelines while Noble gets his inside skills (and Noble's ID is also low, so this could take some time).
What's more, since Noble's JR is atrocious, he's either never going to be an outside SF as you suggest, or Yi is going to end up with some retarded levels of JR (i.e., in the time it will take to get Noble to respectable JR, Yi could have wondrous JR (and a ridiculous salary to boot)).
@the OP:
If they were my draft picks, I think I'd simply concentrate on Yi as a guard for the time being, and let Noble get whatever scraps training throws at him. Just get Yi to where you'd like him, where you're getting the performance you want for the salary you can afford, and let him play for a while in a semi-finished state (there's no race to train a player to his potential cap). Then you can work on Noble's inside skills for a few seasons, and if he were mine I'd aim to make him a nicely-balanced PF.
When that's done, you can go back to training Yi along with a new set of trainees, as he'll still have plenty of room under his cap.