I know they won't add it.

My Idea for a new prop is a team controlled turret (like a sentry, but slower firerate and more dmg) that is invincible and can be used by map makers as spawn protection. there could also be a neutral version that doesn't attack either team until a specific control point is captured. this will encourage people on the opposite team of the turret to take cover. maybe there could be a mortar version as well? I don't really know if this is possible but Its just an idea.

I think there already is a map called air raid... I'm not sure though.