Theoretically you can bail out of a plane from all sorts of angles and maneuvers IF you can extract yourself from both the physical confines and the g forces.
So can you imagine several or a bunch of heavily laden paratroopers trying to get out of a plane doing any kind of steep climb, especially the sudden steep pullouts many C-47s do in Aces High?
Even if the paratroopers were trained for the move, how could they not pile on to each other and get tangled up, or avoid the tail surfaces?
Some might make it out and even remain functional, but surely many fewer than the eight required to capture a base. And if the survivors ever got back to the launch base, I doubt they would thank the pilot for that kind of beating.
A modest restriction on paratroopers being unable to jump if the C-47 exceeds, say, plus or minus 10 degrees from level flight, seems like a quick and easy fix that would preserve fun game play while making it more realistic too.
Same sort of thing that perhaps should be done to prevent heavy bombers from becoming dive bombers.