Yeah, it would be good and natural for the elf-expansion to cater to the themes of Alliance elves as well. It's also not mutually exclusive to an otherwise shared experience against the Void, so they could do this regardless of what happens with the hubs. My Suramar-theory works with a shared hub as well as separate ones.
Dranei's inclusion is grounded enough to be plausible, it just kind of irks me to have them once again as the experts on all things cosmic. Azuremyst and Bloodmyst though... I've played through them maybe once years ago. They didn't seem that remarkable, either in theme or in lore. I was pretty much left with the impression that they're just some islands the draenei happened to crash into. Not to mention they're a world apart from Quel'Thalas, so I'm skeptical about them being included in Midnight.
If we're short on zones for the expansion I'd rather take some otherworldly void zones to provide contrast to Thalassian zones. Maybe have the void elves set up a hub there if separated hubs is the way to go. An abandoned Ethereal city or something? And have large tears in reality connect them to Quel'Thalas, so that we can Dynamic Flight our way there instead of the awful zone-Oribos-zone flightpath nonsense of Shadowlands.