Depends on Ultron's modus operandi. The simplest option would be Vision 2.0 as a single superpowerful robot, slightly ahead of schedule with essentially minimal changes to canon. The interesting option would be heroic!Ultron who still retains all of Ultron's canonical abilities. Bodies aren't important, he's got whole armies of disposable drones with special but ultimately replaceable-if-necessary one-offs made from Klaue’s Vibranium, the Infinity Stone from Loki's Scepter, etc.