Even with an e-conversion you will often have to address the ECU in some manner. Even if you have a full standalone EV setup you will likely still need to integrate some portion of the body harness and fool the rest of the car. Bolting in the crate EV parts will be pretty trivial, the wiring etc is going to take time.

A smart company will come around one day with a targeted selection of cars for a "plug and play" wiring harnesses and control units.