Real talk for a second. We've all seen the fiber controlled drones.
Let's say we replace the fiber with a very thin paired copper wire wrapped in a few strands of kevler, just barely thick enough to handle the electrical transfer and strong enough to not tear too easily; data could be carried through the same cable.
Without doubt this will be more heavy than a fiber drum, but you wouldn't need a battery at all.
Meaning ultimately it's a question of the break even point:
>how much copper wire can you carry before it weights more than the battery
While taking into account that the amount of cable carried decreases with distance traveled.
I suspect the main issue may be the gauge of wire required to transfer sufficient current? Although it may be possible to overcome this quite easily by using the appropriate motor designs; high voltages with low amperage should be less of an issue than 12V 80A?

I guess transferring power over fiber isn't really feasible? It's possible of course but I suspect efficiency isn't too great and optical losses would be too high shooting a fucking kW laser into the fiber.