EDIT: I want to make it clear that this is purely hypothetical, and imagined! Blizzard aren't doing this. I'm wondering what's stopping them.
Now, I understand that back in the halcyon days before The Burning Crusade, resilience didn't exist in its current form. Please note, however, that this isn't meant to be a discussion on that period of WoW. So what would be the positive and negative aspects of such a system? One area where I see a bit of a struggle emerging is as follows: How do you get this gear? How does it scale? Where does the best gear come from?
If I were a dev (with or without my coffee), I'd have to say that one's a tricky one. I suppose you could let people earn points from both PvE and PvP and have them spend those points, similar to valor or conquest now, except both are taken to the same vendor. You could still have lower tiers of gear available for honor or justice equivalents that are easier to reach.