Three wheels have never been a good idea. But the electric part of it may be, I like that part.
I have some questions:
Why did you abandon 2 wheels and opt for 3?
Was that a large enough motor to propel this craft for distance?
Did motor have enough power to move the craft and generate power to the batteries?
Would the next move be back to 2 wheels, frontal steering and batteries in hard boxes?
Do you think that the seat height/center of gravity was too high?
This looks like it has been a very interesting project. I would guess that keeping it lightweight and strong has been a real concern .As with early motorbikes , the powerplant has always been an issue on a weight/frame strentgh plane but, they started off with a proven lightweight bicycle frame. This could be the way to go with that little motor you have. The weight / power ratio would be much better but the shear mass of the batteries could be tricky to balance. Have you considered the 3 wheel bicycle that has been popular with the aged and handicapped? That would have all light weight parts, lower friction tires, brakes,and room for batteries and motor,and the strength to carry it all safely. and best of all you can get parts at any cycle shop. Yeah, I stop thinking about this right now,too many other projects, but I like yours, just needs some tweaking.