Maybe instate of pets, players will be able to control a squad of NPCs, such as light Mechs, infantries or light vehicles (No heavy, mainly because it'll be a bit unfair). You can also limit it to missions or other stuff to prevent players from using them all the time in duels or in some battles. And definitely limit the amount of units. Not too many I say, for example 1-6 infantries. Or maybe give them control of 1 heavy unit. I'm taking this idea from Guild Wars, mainly the henchmen that appeared in GW Prophecies and the Heroes that appeared in GW Nightfall.