>>544708276
40k obviously. That's the setting which lends itself really well to gameplay with tons of cool tech, space magic, enemies, equipment, places and all other stuff space opera needs. And it's an IP easy to get since GW doesn't give a fuck about vidya and so hands it over to whoever asks

Expanse is intentionally shit and boring setting. It's very gimmick is that it's so grounded and mundane there is no that idealized space opera stuff in it. Mankind even failed to properly colonize solar system, can't leave it, can't even terraform planets, armor, tech and locations look samey and generic because anything more cool would be too fantastical. No melee combat and jedi powers or ayys everywhere either
It's not inherently wrong on it's own but it's a fucking terrible setting for a game. It was designed to tell a particular story and not with gameplay in mind. And this game story will HAVE to orbit that original story and be wary to not intrude on it and actual protagonists from that show/book. Won't let you make any actual choices that would shape the world since that wouldn't fit with tv show.
I expect it to be like that Lotr jrpg game at best where you have notGimili, notAragorn and notLegolas which follow in Fellowship footsteps, but can't ever actually reach them or do anything distinct, but they were totally important in stopping Sauron. Or like Telltale Games of Thrones

Those two games should just be reversed. Expanse should be crpg very, very focused on a story and dialogue like disco, because there is fucking nothing else in it. Also make it completely non canon to the show/books and with playable book protagonists so you can actually make some decisions. And not the way they make it

Their 40k game should be an action rpg with AAA values, combat and explosions everywhere and other stuff like this. This is what 40k was designed around. Rogue Trader in particular would work great as a Mass Effect clone.