Any chance the gems will go into more items than jungle items?

Gems? Gems are truly outrageous. They are truly, truly, truly outrageous.

I see it as roughly similar to the Boot upgrade mechanic.

It's worth pointing out in both situations that the upgrades are for items that will always be picked in their basic state. I'm not sure what other items would be a good fit for that model. Maybe the Doran's items, but those are specifically designed not to be upgraded.

The only thing that they would probably work on is some redesign of the support items.

I like the "pick a stat" thing, but they can't just stick the same things on and IE and Triforce or whatever. Those are already expensive top tier items, what's the point of making them even stronger?