Would it be possible to add to the "Find an upgrade" function a means to pretend-equip the upgrade and see what effects the item would have on your character?
So for instance, I click find upgrade, go to wowhead and look for the upgrade I'd like to aim for, copy the item's code (12345) and return to wowhead, enter it in a field somewhere and change my stats according to that item?
The only good solution I've seen to this is what the people at warcrafter seem to be doing, which is to "sandbox" the character. It seems to involve taking a local snapshot of the toon, as is, and then pulling the data from that snapshot instead of the armory cache, which lets them switch out db entries on the local snapshot. That's just my best guess as to the actual mechanics, but it does seem to work.