The problem with any sort of nano tech is you always come up with the same question over and over. "why do I need to implant it when I can just wear it?" If you can make glasses that see in the night why modify eyes to do the same? It's much easier and cheaper to make 1,000 pairs of night vision glasses than it is to perform surgery on 1 guy who may reject it or even go rogue. Nano tech in surgery makes sense, it's a fixed 1 off event that needs to be dealt with, but mass produced nano tech surgeries doesn't. And any sort of super soldier you made is still going to have a critical weakness to bullets, mortars and air strikes like all the rest. Much better to give the grunts equipment so you can switch them in and out while other tech does the heavy lifting. Bomb everything to death and send the grunts to the crater is a much more effective tactic than spending a decade perfecting a super soldier only for the enemy to have left a trip mine that blows his leg off and leaves him crippled.