Games

I am serious. With some slight tweaking, there's some fertile ground here:

• Set the game on a populated Mars instead of Phobos/Deimos to preserve the basic game structure of intercept enemy ships/respond to terror missions/take out bases
• Plasma rifle/BFG 9000 as early game research options (equivalent to vanilla X-Com's laser rifle/heavy laser), use Doom 64's Unmaker and demon weapons as inspiration for late-game tech (heavy plasma/blaster launcher equivalent)
• In Doom and Doom 2 alone there's enough baddie variety to have a suitable roster of enemy units
• Even though the games mostly have heavy metal soundtracks, there are many songs that would make suitable geoscape music
• You could recreate the revenants' homing fireballs by just taking the blaster bomb code and reducing the explosion size/power
• Final research is opening a portal to Hell, final mission is invading Hell
• Absolute bullshit like a cyberdemon reaction firing and instantly wiping your squad would both preserve the authentic X-Com experience and reflect the effectiveness of non-Doomguy marines in Doom's lore

If only I didn't have a million other projects I already wanted to do.