It would depend on where you are. The laws vary from country to country and in the US from state to state. I think it would be the motor actually attached to the wheels and moving the bike that would count as assisting the bike. It would be a heavy set-up, as both the electric motor, battery, and generator/alternator are fairly heavy and the engine driving them has some heft of it's own. Eliminating the battery and driving the motor directly off the generator/alternator saves a little weight, but not enough to offset the addition of the gen-set and it all may be considered as part of the power train in some jurisdictions. If they want to get fussy, including it as part of the power train instead of as an electric transmission, they could add the power of both to outlaw it. I don't like the complexity or added weight for everyday use. It adds maintenance and extra weight that strains the bike. I have considered putting a gas or diesel engine driving a generator/alternator on a trailer to recharge the battery on the fly to allow longer trips on my e-bike. That way I'm not straining the already heavy e-bike when the trailer is disconnected and I'm just riding around town.
