I know invasion storylines have been done to death, but do you think now would be the perfect time to have NXT invade WWE? If WWE treated NXT as something special that is ONLY available on the WWE network, I think it would sell many people on the network. I mean they should still keep it as the developmental show but there are enough wrestlers on the show that can have 10-15 minute matches on Raw already. They would basically be debuting 10-20 new wrestlers at once, but they don't all need to get regular TV time. With Night of Champions supposedly being the second most important show of the year, they could even have Adrian Neville defend again John Cena as the start of the storyline (with Brock v. Roman Reigns as the other big match).
Honestly, there's just not a lot of depth in NXT to bring up that many people. Plus then you're paying out a lot of main roster money instead of developmental money and it's a big investment without a lot of upside. They've been "prepping" the Ascension for a year and a half now and they're STILL not ready yet, for example. Bringing up Neville will immediately expose him for being smaller than everyone else and probably kill him off. NXT has been struggling to find its own direction as of late, and now would be the worst time to gut it further.