To be honest I was surprised that no DoomxWarcraft crossover had been made yet. That's why I am putting this up. I would do it, but my knowledge on Warcraft lore is minimal at best. Anyone can do the challenge but there are rules:
Doom Slayer's background: I think him being the leader of the Night Sentinels is a must. And he should be the one who had betrayed his comrades to revive his son, as the demons backstabbing him would be a good motivation for him to eradicate them all, as it cost him his son, comrades and home.
Arthas: He should still become the Lich King since it is the best way to tie the story in.
VEGA: He should also be there. He could be downloaded into the Praetor Suit.
Burning Legion: Obviously they would know and fear the Doom Slayer as all demons do.
Army of Light: Optional. They could be familiar with the Doom Slayer, even having fought alongside him against the Burning Legion.
Night Elves: Again optional. The Doom Slayer could have been on Azeroth 10,000 years ago, helping the Night Elves against the Burning Legion's first invasion.
Doom 3: I feel like some elements from Doom 3 could be in it. The Doom Slayer could be depicted as the Martian Hero, having helped the Martians. And remember, the Soul Cube was found Doom 2016, so you could have that in the story too.
Demons: Along with the demons from Doom 2016 and the Burning Legion, you can include the ones from Doom 3 and the ones shown in Doom Eternal and the other Doom games too. Add in more fodder for Doom Slayer to kill.
Pairing: This is optional. You can pair Doom Slayer with any of the women from Warcraft, except for Tyrande. Just make sure the reason is good enough.
Crucible: I feel like Doom Slayer should have a melee weapon besides the chainsaw. Plus, it would look cool if he had managed to take back the Crucible before Hayden teleported him.
If you're interested, leave either a review or PM me. I hope to see some stories soon.