Niche market potential
It appears there might be a decent demand for a cordless battery operated chainsaw in the "pro" class. I just looked at what I could find, just little tiny homeowner capable saws for very light duty, all under a hundred bucks. If there was like a $300-500 or so quality saw..perhaps it could sell. I would imagine such a saw would needs be 24 or 36 VDC, along those lines.
As to charging batteries on the jobsite, without having to plug into the homeowners outlets or running a genny, a second (or third..) deep storage battery installed in your truck with an "isolator" circuit, then a large inverter would do it (or rig your own charger straight DC..beyond this discussion right now). The isolator is what they use on campers/rvs so that the alternator charges both the starter battery and the deep storage "house" battery when you are driving, but use of the house battery does not run down the starter battery at all, it is "isolated" hence the name. They work fine, have two of them, one on my camper van, the other on my small full fledged rv.