It awesome yes

I'm not a major fan of The Dragon King and felt that Deception kind of botched the story, but I'm not opposed provided it's a good game and made with care. He hasn't been done "too much." But I wouldn't lose sleep if he never appeared again.

I think we're in a white place where nostalgia for the 3D era games is starting to creep in. MK9 was lately a love letter to the classic series, so I could definitely see Onaga getting some attention in the next game.

He does have unexplored potential and would make a decent boss but then I don't remember ever radically digging him (admittedly, I was happy with him making the short work of the Deadly Alliance and, especially, Shao Kahn in MKA intro). As boring as Shao Kahn grew with time, I still think the "Outworld tyrant" role fits him best. It would be fine if he underwent the same overhaul as did Shinnok in MKX, though. The latest hints of his power somehow finding its way to Shao Kahn and Liu Kang might re-spark the interest in him, too.