I still think a trike would make a great DIY hybrid vehicle.
Get a motorcycle with a working engine and transmission, mate it to a front wheel drive car front end - put an electric motor and batteries on the front.
Poof! A hybrid that can be pushed with the motorcycle engine and rear wheel or pulled by electric power with the front tires.
Here's something similar:
Look close at the black and white photo in the upper right. You can see it's just a motorcycle and front wheels put on there.