I thought about 1x1 UGVs pros and cons and ended up with an idea (yes, I know you have plenty of them, but still
). What is the main difference between soldier and 1x1 UGV? Firepower and toughness. So, we take a soldier, give him heavy armor with exoskeleton (IIRC we have proposals for those), and give him more powerful weapon. And here comes an idea: make this weapon with backpack - like in "ghostbusters": some kind of accelerator with power supply on the back (weight doesn't matter as we have exoskeleton), and some kind of ejector in hands. Like this it can be done more powerful without "realism" issues. Will do for "heavy particle weapon" or "heavy plasma" or whatever.
The resulting unit won't differ from 1x1 UGV in any way, and still be a soldier.