I'm just throwing this out there, but maybe there was an equivalent to what "Supersize" meant for going larger in size instead that's geared towards plant-based versions of each burger. So maybe I still want a Big Mac, but I want it with these plant-based burgers but still with the extra slice of bread and the special sauce.
I don't have a name for this as clever as Supersize, but it seems feasible.
Why?
Their burgers are BigMac, Quarter Pounder, (and Quarter Pounder WITH stuff), Cheesburger, McDouble, Hamburger, McChicken, Fillet-o-Fish.
While "Mc" is the start of some of the names, it's certainly not a must.
I would have gone with "McMiracle Burger" (as a riff on "Impossible Burger").
(McDonalds is working with Beyond Meat, one of Impossible Foods' largest competitors, for their plant-based meat substitutes; deriving their product name from a competitor's product is almost certainly a bad idea.)