i once took over a story for a guy with a similar premise, tho not in the same way. Basically it had all these different pantheon of gods existing, not just Olympians. There were the Aesir(Norse) and the Tuatha De Danann(Celtic) and other ones. They all existed in the universe and went about claiming planets, i think? Anyway, they had territories throughout the Mortal Planes, basically the universe as a whole.
it didn't really center around a demigod character, just some bullshit OP MC whose origins were never really explained except that he reincarnated every so often. He MAY have been a Primoridal? Dunno, was never said, it just a theory i had for him since he was so OP even compared to other strong characters. The actual plot didn't revolve around the pantheons, but i do like that they had a place in the story. Lol i loved his Loki character. MC was friends with him, Solomon, Ares, and Astaroth. They were all pretty fun characters, i say, tho the MC was a bit too strait-laced.
When i took over the story, i changed that. Dont think ever made it past 16 chapters cuz i was busy with other stuff and just forgot it.
But i digress. Yeah, that aside, it was a bit of a Xianxia-styled story, maybe? Mixed with a bit of Isekai? Because it didn't take place on earth, but earth did exist and was mentioned a few times. I dunno, i liked it. Least enough to take over the writing for it when the guy stopped updating....then i stopped updating it myself....heh.
I like the idea of it tho. Everyone always makes these kinda stories restricted to earth, but these are GODS. They should be all spread out through the universe and shit, with their own territories and whatnot, and the original author brought that to life for me. While i had gripes with some of the writing, like info dumps, overall i felt that the concept of all these interesting pantheons existing together was neat.