Whys no one mentioned actual FPS-RPG-MMOs yet?
Fallen Earth. First person post apocalyptic MMO with quests like WoW and FPS combat with guns. Standard problem that the hit detection was horrendous and I couldn't play very long before getting horrendously bored.
Firefall. Much more promising, and currently in beta. Jetpacks and Guns and cartoonyish graphics, in my opinion it seemed like an excellent start but my problem was there wasn't a lot to do. The teamwork of finding a harvester thingy and everyone comes along and helps out and gets loot for it was like Rifts rifts, and they were an excellent way of doing MMO FPS teamwork. But that's all there was in the game really currently when I tried it.
I think Planetside is big enough to be massively multiplayer, but not big on the RPG fronts or anything like traditional MMOs, FE and Firefall are.
The main problem these games face is hit detection and net code won't be as smooth as BF4/CoD/TF2 ect with a stupid amount of people, once a company comes along and fixes that the FPSMMO games will be amazing. Till then you're subtracting game feel for a huge amount of people, and both are fun but together would be something special we haven't got yet.