His kit would be that there is Ultron and 3 actual Ultron drones (not these Temu drone BS) Ultron has 350 HP and each drone has 200 (or maybe a little less). You have to kill all his drones to kill Ultron. If you kill base Ultron you just hop to control one of his drones, and then the other until all are dead. The drones are hard mode AI controlled and can be healed and killed just like anything else.

Ultron would effectively have the HP of a tank but split up between multiple bodies. He would be able to command the drones to focus their attacks or defend or even form a wall and protect the main Ultron. If drones die they can be brought back to life with an ability that requires the Main Ultron to be focus healed basically Transferring that healing to the hp of the new drone. But only the primary Ultron can revive drones. He dies you have to respawn to get that ability back.

Ultimate ability would send out all drones to lock on to targets (a la Smart Pistol from Titanfall) and then fly into them and self destruct for big damage and a very brief stun then immediately regenerate all 3 drones. 

(Also if you gain Ult while in control of a drone Ulting brings the primary ultron back and you swap back to control them.)

The kits of the drones would have less abilities than the main Ultron and be slightly less effective in combat etc.

Ultron should have always been a Vanguard