Raiding alien infiltration operations
This could be an interesting type of mission.
Have X-Com raid a multi-story building where the aliens have set up an infiltration operation - headed by Thinmen ofcourse. Have civilians in and around the building and perhaps even have human combatants under alien influence/control that you have to fight.
I liked in apocalypse how you could raid cultist buildings and how you mostly fought cultists but occationaly found aliens hiding with them.
Would add some nice variety and possibly some new challenges, such as avoiding collateral damage to civilians
Devs. have talked about "multi-story" not really working.
Human enemies is a concept I hope they bring up in a sequel (Sirius works perfectly for this), but collateral damage is nothing new; you have the same mechanics in Terror Missions. Avoiding collateral damage is just removing the targeting of civilians by aliens, and not to have your soldiers use AoE weapons in close proximity to civilians.
Not a well thought out suggestion imo.