The G26 Gran Coupé is the four-door 4 Series from 2021, and the most useful thing about it is not in the brochure: the electric i4 is the same body. BMW did not build it as a separate model but on the G26, and the two come down one line in Munich.
Doors, wings, roof, tailgate and much of the interior are common to the combustion car and the i4 and work in either direction, which widens the pool of possible donors considerably. The differences start where the drivetrain shows through: front apron, the i4's blanked grille, underbody, cooling, and a charge flap where the fuel filler would be.
As on the F36 before it, the Gran Coupé has a large tailgate rather than a boot lid. It carries the rear screen, is heavy accordingly, and has its own hinges, struts and usually a powered mechanism — nothing about it matches a G22 coupé's boot lid.
At the front the G22 and G26 are the same car, front doors included. There is no M version of the Gran Coupé. Doors are what we strip from this model most, along with front wings and headlights.