Well, as a game features a protagonist who - in another game kills God - is aided by a senior commander of that world’s forces who is a woman who is revealed to possess great power, the fact that said protagonist kills no less than Cthulhu himself is money going to id Software for seeing such during “DOOM: The Dark Ages”.
id Tech 8 can really visualise such in great detail too. I’ve seen here & there people going into great detail re. ‘What If’ Doomguy was in the “WH40K” scenario: perhaps via a slipgate malfunction? But he wouldn’t mind. Demons from Hell or the Eye of Terror, ’tis no difference to him.
But considering what happens at the end of the 2nd “DOOM Eternal” DLC, I’d pay good money to see what he does to Khorne, Tzeentch, Nurgle & Slaanesh.
…and as per the Night Sentinels led by Valen - a black man - in the final assault on Davoth’s forces at Immora, he would do so no doubt with help from the various Loyalist Space Marine Chapters: none more so than the Adepta Sororitas.
Would also be fun if, say, the Adeptus Mechanicus were to create a portal to the Webway for him: certainly to Commorragh, he being true to his name: the Slayer. As he massacred all of the Dark Eldar.