On Gatlings in WW2, for shipboard use, someone else pointed out the dangers of ships losing electrical power (the South Dakota comes to mind).
For aircraft, however, far more than electrical power or CG issues, recoil stresses are your worst enemy. Gatlings are not so much larger in a dimensional sense, but they are considerably heavier and a conventional MG, and firing any kind of extended burst is likely to warp the wings on anything smaller than an A-20. That said, a 20mm aborad a B-25 would be pretty devestating, but you would have to evolve dive-attack tactics, as the "racetrack" profile is a recipe for a shoot-down, until the very end of the war.
The lead time, depending on which Power you're giving this to, is going to be 1938-1942 at the absolute latest, IOT get it deployed in any significant numbers....