I have a crazy UGV idea of sorts...
Think like this:
But with a payload.
The basis for this idea, is sheer common sense. if it were me, I would send my Christmas bonus on a cheap old RC car which I can drive into an alien ship ahead of me, and if I had a couple of grenades going spare I'd invest in some gaffer tape, a webcam, and a remote detonator.
Bingo, an expendable (and fun) asset. Park it in a harvester stairwell, wait for the alien scum to come down the stairs, and Goodnight Vienna.
The idea I had was, you give it a fixed range for the duration of a mission (say 120 points) and once it's gone that's your lot - all you can do in any subsequent round, is detonate. However, you should be able to detonate it at any time, provided a soldier has clear line of sight.
As for the payload, it would have to be sensible - totally annihilate any living thing in an adjacent block, stun anything within a 2 block radius, intimidate any alien in a 3 block radius, and of course destroy the toy.