Elevator room can be a bitch to take down.
If humans build teslas a bit farther, it becomes very hard to snipe them. And as soon as you jump up there, teslas push you back and hit hard. Having turrets a bit farther means it's no longer a pleasure to get into their base. Very hard for marauder, especially if you concentrate teslas near walls (you have to use walljump to get there).
With right weaponry (pulse rifle, shotgun, flamer but you need to be careful with this one, cskit, GRENADE) it's still very hard to beat.
If I see aliens under balcony, I throw a grenade there. Boom. In worst scenario (where you just buy a grenade and make a suicide run) it only takes $200, and often earns you much more.
If you're dealing with elevator room, be sure to seal the vent with a tube/hive and an alien (marauder) or sth. It's quite unpleasant otherwise, and humans can relocate.