Well, you will have a friction loss on the drive train, you have additional rotating mass as well as additional dead weight - this all will absorb your watts into the system with a lower watt percent available for spinning the prop so you will end up with bigger batteries. The suggestions are provide the most efficient and simple way to power a large electric. The one place I still see smaller higher KV motors useful is using geared in-runners when you have a very tight mounting area like some smaller turbo prop scale applications or a performance sailplane.

it's really quite surprising how small (weight and volume) a good out-runner is compared to the equivalent petrol IC engine.


as for not addressing your power source for battery charging:

I mostly keep enough sets of packs that I don't need to charge on a day I fly. I charge at home starting a few days before a planned flying day using a very large power supply on my CellPro10 supplemented by a few other chargers for smaller and Nickle based packs. My primary club field has installed a solar collector and Pb/Acid storage and we often charge packs at the field from that. I do know some fields have A/C power available and I've often seen personal petrol generators in use at events. I personally used to charge smaller packs (3S 2000mAh) off my car battery however between fear of running the car battery low and damaging it (not a deep cycle) and fear of LiPo thermal-runaway fires (most of my packs have experienced some bumps and bruises - never had a charging fire yet) I have stopped that practice.