Folks probably won't have as much of a need to go from main roster WWE to NXT as they used to, but having a non North American soccer promotion/regulation system would be an interesting concept.
People in the bottom tier of WWE get sent to NXT where maybe they find that spark that gets them back in the bigs.
People in NXT who catch fire get a shot at the big stage to see if they can hang, and if not they can always go back down to NXT as a returning hero.
Conversely folks at the bottom half of NXT who maybe aren't quite ready can go get reps on Level Up until they have enough of a basic understanding to not get embarrassed on national TV.
...and of course like in soccer, someone dropping two tiers would be "a serious of major, yet also hilarious, fuckups have occurred" kind of thing.