Hmm...I'd probably have the PC make a Jump check against the target's AC. If the PC succeeds, the foe and the PC both take the falling damage. Maybe they each take 1d6 less. That way, jumping on someone from 10 ft. up is basically a charge, from 20 ft. you each take 1d6, etc.
Crush (Ex)
This special attack allows a flying or jumping dragon of at least Huge size to land on opponents as a standard action, using its whole body to crush them. Crush attacks are effective only against opponents three or more size categories smaller than the dragon (though it can attempt normal overrun or grapple attacks against larger opponents).
A crush attack affects as many creatures as can fit under the dragon’s body. Creatures in the affected area must succeed on a Reflex save (DC equal to that of the dragon’s breath weapon) or be pinned, automatically taking bludgeoning damage during the next round unless the dragon moves off them. If the dragon chooses to maintain the pin, treat it as a normal grapple attack. Pinned opponents take damage from the crush each round if they don’t escape.
A crush attack deals the indicated damage plus 1½ times the dragon’s Strength bonus (round down).

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.