OK, so Rivals have levels (4), and they got a little bit more HP, but they could do better - give them some skills …skills that would get stronger or more additional skills with each level.
For example:
faster ROF
faster movement speed
concussion pulse on FNIX Tanks/Harvesters or smaller machines
seeker comm array
upgraded vision and player detection
bigger gas puffs
smoke screens
etc.
And one more thing - skills should be anonymous until used against player