I have always admired your bike, it is obviously a work of Annie.
I have had several front hub motored bicycles and I always considered them to be 2 wheel drive as one is able to churn the cranks to transmit power to the rear wheel(s). They work really well in snow and I know that from experience traveling frozen snowmobile and groomed XC ski trails back in 01'. I never could get enough out of an SLA system though to satisfy my needs (especially in cold weather) although I pedaled at the top of my gearing at all times I couldn't get any more than 30 miles and when you are having that much fun 30 miles (2 hours or so) is not enough. But with the gas engine charging a lighter battery like a NiMh or Li Ion and having enough storage in that battery to operate the electric alone for a decent period, say 10 miles or so and have enough for the lighting system and electric start and onboard compressor, not that much added weight
. 2WD Euipped MAB's will be in the vacinity of 70 lbs. and hopefully less but losing weight via components etc. on a MAB is not as crucial as the ones I maintain for pedaling in the forest where I am solely responsible.
A decent tandem will handle two 250 lb individuals and the stronger ones weigh in at 50+ lbs so my 180 lb. loaded body on a 70 lb. bike should be able to carry an additional 300 lbs of weight before things start needing to be re-engineered?
And also I like your modular carry all system. It is what we are trying to strive for also. If you notice the large post holding the front of the rack on the raw bike in the picture that is our central mounting point but nothing more than a standard seattube that will hold a 27.2 seatpost or its equivalent. It is very solid and any manner of rack can be assembled around it and using other contact points on the frame as well. Plus we have a tandem that just happens to have a 27.2 Cane Creek short travel post in it with a Brooks Contessa brass rivet saddle and a 27.2 front saddle with a stoker grip set up on it and when I get my R/S bike going we are going to have to slap it all on there and try it out.