Age of Empires 2 is a top tier, all-time success of gaming. Doom is also a top tier, all-time success. Modder HELLKNIGHT61 was aware of both of these things, and they have used the Age of Empires 2 engine to make Doom into a third person, isometric RTS... shooter... thing.
"I wanted to resurrect the original DOOM for Age of Empires 2 game engine," HELLKNIGHT61 says in describing the mod. "This was my dream."
The Age of Doom mod for Age of Empires 2 is a campaign that ports ideas, themes, and bits of story from both Doom and Doom 3, sampling audio and enemies from both. Most notably, it ports sprites, projectiles, and effects from the original Doom into the Age of Empires 2 engine. So Doomguy walks around and uses a super shotgun, sure, but there are also cyberdemons and pinkies and everything else you'd expect to see. It has its own tutorial and a four chapter campaign, with a fifth chapter yet to be released.
The whole thing reminds me of the days of Warcraft custom games, to be honest. Is this something you should try to do with an RTS engine? I don't know, but HELLKNIGHT61 has accomplished the dream—who am I to deny it? You can find Age of Doom on ModDB.