Destiny is a shooter with lite RPG elements and not an RPG with lite shooter elements, though. You want an MMORPG, which is all well and good, but it also isn't Destiny; Destiny's simply a shared world shooter.
I think set items would be a good introduction, as long as they're not the Diablo III route of being 6pc, because then you just reach a point where you can't mix-and-match so well anymore, but 2pc/3pc bonuses would be cool; three artifact slots in lieu of rings/necklaces could work, too.
What did you have in mind with "Artifact"-tier gear? Is it just exotic [i]but better[/i], or is it something interesting and more than that?