While a 5/5 indestructible beater sounds like a reasonable threat at first glance, considering that Historic will likely heavily feature Teferi, Hero of Dominaria, Teferi, Time Raveler, and Oko, Thief of Crownsall of which incidentally answer a 5/5 indestructible Darksteel ReactorI'm not sure the plan will actually be competitive
Essentially, this means if a creature has haste, you can attack with it the turn it enters the battlefield
1 Niv-Mizzet, the Firemind
Red decks need their removal to be able to go directly to the face, which is the one thing you cannot Terminate, and while being cheap is nice, the creatures you need Terminate for don't come out fast enough to reward you much for it being so cheap