Simple and easy to use would be helpful. Maybe a drop in square tube like a Moore 24 (or other Santa Cruz uldb) and a modified mount on motor, with a hinge so it stows easier. The Moore uses a square tube to keep mount from rotating.
With less force in electric motor, a round mount may work with a pin and slot to keep it from rotating. Be sure to drill hole at bottom of receiver to let water drain.
The square Moore receiver was tapered to release from mold. It seems two concentric tubes may offer more simplicity.
The transom seemed to have access ports in each hull section. The receiving tube could be mounted off-center on one of the cockpit walls.
I like the use of wood to re-fabricate the motor assembly. The fun of creating (as AlanH knows well)!
Ants