I think if we create a UGV with better armor and excellent long-range accuracy, then nerf the human tech weapons, we'll just end up turning the UGV into a super-soldier, making other soldiers less relevant. This is the balancing problem I was asking about.
Sorry I wasn't very clear. What I mean is in general the rule is, you have to make the player's options less effective to make up for the AI's dumbness. So if you add a human heavy UGV "tank", then you have to give it 75% or the armor and 75% of the firepower it would have if the AI was competent or this was a multiplayer only game. Or give the aliens more powerful weapons, like an early game tank and anti-armor weapon of their own.
Then later on, when the AI becomes more smart and modern, using heat maps and such, you must rebalance the arsenal's stats more in favor of earth weaponry. But whatever you do, UGVs don't make any special difference, you just have to balance them up or down for the AI, like you would any infantry weapon or equipment.
Your ideas around the scout UGV are interesting -- particularly the remotely piloted bomb. We'd have to get the economics right on that one so it wasn't too easy to just buy 1 or 2 UGVs to blow up each mission. But it could be an interesting piece of equipment to deploy in special circumstances. The main difficulty will be figuring out how to keep it from rendering Close specialists obsolete.
Because it takes up an entire soldier slot, can only be used once and has no ranged ability whatsoever (versus CQC specialists who can carry a laser sidearm for example).
My main consideration when I consider "balancing" issues is: how do I add to the arsenal of options without making any existing options obsolete? Close specialists are a difficult breed to keep useful, because they necessarily run higher risks and have more narrow utility. The return on investment needs to be higher than, say, an explosives expert who can do alright in the open or indoors or even indirectly.
Well that's where a "breacher" UGV comes in. It goes on point during room clearing and takes the brunt of the alien ambush, possibly sacrificing it's nonliving self, and then the CQC specialist(s) follow immediately behind and do a lot of lower risk killing. That would help one big problem with using CQC specialists, that they don't survive well.
The other problems they have are not directly related to UGVs. Probably hand grenades and grenade launchers are too effective, and thus effectively replace CQC weapons. Or that CQC weapons cost too much TU and do too little damage to make up for such limited range. Or that there aren't any good long range side arms besides the laser pistol. Having UGVs can't help or hurt any of these potential imbalances.
In general terms UGVs are semi-expendable super-specialists. When they die you only lose money, not experience. And while they generally can have a better something than a human soldier can carry, they are also bound to it. A CQC or fire support guy can have a rifle, a sidearm, a knife, several hand grenades, and can pick up other weapons/ammo from fallen comrades and aliens, all in addition to his staple weapon. He can quickly shift from one role to another on the battlefield. But UGVs are locked into using one weapon, maybe two. They are committed to doing one thing especially well versus a non-veteran human specialist. And so they make you think more carefully about their deployment, both before you launch your dropship and while in the battlescape.