Five mana for a targeted pump is a rate the format has to forgive, and a medium-speed TMT mostly does. UR Artifacts is the obvious home, landing this at P1P5 to P1P7 as its top end: a legendary anchor that seeds its own board on entry and then converts every subsequent combat step into a tempo swing the opponent has to answer with removal they would rather hold for a Turtle. The self-replacing Robot is the load-bearing detail. Cast this into an empty board on turn five and you untap into a 4/1 first-strike vigilance attacker plus a 3/3 that still blocks, the exact profile that wins both directions of the race against the 
2/3 commons clogging the ground. You never need a second artifact creature to make it work; the body it brings is the one it buffs.
Both Izzet builds want it, but for different reasons. UR Artifacts takes it over a second Bot Bashing Time: Mechanized Ninja Cavalry and the steady stream of Robots and Servos give the combat trigger a deep pool of bodies, and vigilance keeps the buffed attacker home to trade. UR Sneak, the Disappear shell, values it a touch lower, and not because flickering wastes the trigger: re-seeding the Robot is real value. The drag is that the combat anthem is stationary, and a deck flickering for evasive reach would rather its five-drop carry the payload in the air itself.
Killing Baxter with the trigger on the stack does not punish you. They spend removal, you spend Baxter, you keep the Robot: a one-for-one you come out a body ahead on. Maindeck in any UR build.
