That's what I mean — you can create superficially-similar Demon Forms that aren't actually Demon Forms, but either you're gutting something about Demon Hunters (and disappointing people) or gutting Demonology (and disappointing people). It can be done effectively, I just see it as unlikely given how Blizzard designs and especially how conservative they're becoming with 'disturbing' people as WoW ages.
If you look at DK for example, they kept everything core and identifiable about it (from WC3 forward, I mean) and just expanded. But DH has had all of its pieces dissected and redistributed, so while you can make a very cool class in Demon Hunter's image, you can't really make the Demon Hunter people are fond/nostalgic about.
Monks had the advantage of being mostly uncharted territory, and (amazingly) having none of their concepts distributed to other classes in the ~8 years before they were introduced.