Nanite System Ops are robots...and it would only make sense that when a bot dies, the engineer should revive it and heal (fix it) instead of the medic?! There can be medic bots to tend to human soldiers, but engineers should tend to robot soldiers!?...
Yeah I found it a bit odd that medics are reviving bots instead of engineers. Probably a way to ease the transition but it would seem to make more sense to make it distinct from the other factions. Plus it would boost the need for engineers which seem to be an underused class. Personally I love playing engie as the class is so versatile and can solo roam with ease to take out hidden sunderers or zip to a flank and set up a turret and really screw up an armored advance by targeting the weak rear armour.
While it's a bit of a plot hole, we probably won't be making this change as it would fundamentally alter the function of engineers as well. For now, medics are just really talented at healing, be it a soldier or a robot.
Don't tell anyone but really we're all made of the same stuff; Nanites. You? Nanites Me? Nanites That tank? Nanites These bullets? Nanites Those NSOs? Nanites We're all just different arrangements and patterns of nanites.