There is already an alternative to rookie troops, in the forms of the automated tanks. More armor, more TUs, and heavy weapons in one platform, with no monthly salary or need to micromanage equipment. Of course, the trade off is they're expensive, large, only a few go on the mission, don't really get better (indeed if they get the kills, the rest of the solders don't advance...) etcetera.
Perhaps what we need is something like the modern
TALON/SWORD combat robots rather than elite troopers. Arpia already made a
scout drone mod - give it an assault rifle rather than a smoke launcher, up the cost a bit, and there you go.
Since these are remotes operating on cameras (and in 1999, not even mega-pixel class digital units yet) even if they're cheap, they're not accurate, and have fairly low TUs due to limited control schemes.
To make this even more strategic, maybe there are a few different types of drones with specific specialties, so you need to pick and choose what you have. A standard Talon is a decent shot, but has no reaction fire ability, while sentry guns have high reaction and a sniper rifle, but don't move fast. Bomb disposal drones may be able to plant heavy explosives/grenades and have electronic disable units (ie stun rods) but no ranged weapons. Human soldiers have greater adaptability.
Unfortunately, I'm not all that good at programming, so I can't make a complete mod for remote robots myself, but if someone wants to take this and run with it, you have my interest.