Okay, I'm a little late on this, but oh well.
First off:
Actually... there already is one. Granted, not completely lagless, but if you short hop, do a fair once you reach the top of the jump (approximately, I have a hard time describing exactly when to pull it out), then hold down the moment Ganon shouts/yells/whatever the hell he's doing, then he will come crashing down with his fist. However, if you hold down before he yells, the animation will happen but no damage will be done. Also, since you accelerate to the ground, for some reason the landing animation is shortened (or so it seems, though it is MUCH more obvious on the Nair.)
As for strategies, Nair, my new favorite Ganon move. I was experimenting in Training yesterday, and if you do the same thing described above, only with the Nair, you can do a quick kick with almost no landing lag. Also, since you land in a crouch, you can easily follow up with a dtilt to stutter step fsmash at lower percentages. On top of that, the closer you get to the ground before hitting the Nair, the less time it stays out. You can actually make it so the move barely flashes on the screen (It would in that case only even show up as an actual attack if you hit something.) I love it as a way to move forward, as it cancels most projectiles, MK's tornado, and is decent for setting up combos. Also, since most people expect you to attack as soon as Ganon leaves the ground (like when you thunderstorm), they rarely expect a quick potential combo-starting attack as you get back towards the ground.
However, I have only been trying it against comps, so someone try it against an actual player and tell me if that actually works against humans.
(I haven't seen any videos/mentions of this so far, so I'll try to get a video to illustrate what I mean when my friend lets me use his camera.)
Hopefully this turns out to be as good as I'm making it sound... Works well against comps in any case.