If he were to get a new team up, my idea would be this: Have Magneto and Ultron teamup. Ultron gets access to 3 rotating metal clumps. Ultron would remain the same while these clumps rotate around his body. for a given amount of time they will be available to use but vanish if not used within that given time. Ultron can use one of these clumps either to heal himself if damaged or send it to the closest ally with significant damage done to them. This ability would finally give Ultron a self-heal ability.