I want to see a drone pull a pony express and swap batteries on its own over a flying course. Of course I don't mean just installing an onboard switch or something. And almost as cool would be watching a gas powered rc plane refuel in flight.
Comparing the gas model and the electric model is fine if you just remember that the battery is comparable in function to the Gas tank and the battery charge is equivalent to the gas itself.
Perhaps an external charging circuit from an external battery source would be a better option than swapping out "Gas Tanks".
Knowing the current used by the craft in flight and the maximum fast charge rate of the flight battery you could find/design/make a current limiting fast charging circuit with an allowance of extra current for the craft flying current usage.
With a little more sophistication you could also include either a voltage limit to the charge circuit or even have the chanrge cirsuit carried on the craft itself. With the charge/run current circuit sorted out and possibly on board the craft then all you would need is a method of connecting to a high current power source in the correct polarity. Therefore the "Towing" cable could actually be the high current leads to the craft charging circuit.
Technically once all the number crunching is completed it could be possible to have the craft perpetually airborne as long as ground based current sources could be accessed.
The same arrangement would also be applicable in Air to Air refueling of conventional Electrical RC aircraft.