You’d need to add back in an all wheel drive powertrain. A typical drive shaft is 20 to 50 pounds (9 to 23 kilograms)

The motor is high torque, so I’d expect the drive shaft to be on the heavier end of that.

I’m not including the other power train components, but it’s easy to imagine it all adding to more than the weight of a second engine + wiring.

Also, having one more complicated power train is probably less efficient than two simpler ones, which implies a bigger battery.