Everyone ride down? Huh, interesting.
Not the way I've seen it done a couple times over the decades.
Just contain it out of the way and others jump.
Although admittedly if others jump, that is a bit of a, "Screw you you dumbass, you can sit there white-knuckle clutching your damn parachute, we're going jumping like we planned" move....
Or in more detail, keep door closed, contain the parachute, shuffle the guy to the front of the Caravan for example (far from the door), then the guy stays in the plane (plus an instructor if he's a student), others jump. It's not hard to hold on to or sit up against a spring loaded PC or a bagged main, holding it against a wall or bulkhead. Or if it is a C-182, get him to the back corner and the rest could jump. Although there can be variations depending on experience levels, like deciding it is safer just to descend with the full load in the 182, because it is cramped or moving a scared student could be tricky or whatever.
Sure one is assuming someone else isn't going to take the tail off on that very same jump run and leave the unfortunate jumper with an even crappier than usual situation!
But certainly everyone riding down is a valid thing to do.