It would then be off balance, it appears to only have one rear wheel, having something heavy enough on one side will throw balance off, there needs to be a way to keep the balance as center as possible.
That is kinda the reason I suggested a high torque, high speed 12v motor and a 12 battery pack, or a bank of batteries he can haul behind him in a wagon :3
If he could optain some really high cranking amp batteries, I am talking 2k+ that are relatively small, he can got for awhile with out them dieing.
I know its a bit different, but my 1k cranking amp battery can power an amp that pulls 70 amps of current @ 12v for about an hour, so I think he could easily do it if he gets his gear ratios right, and the right DC motor.