I agree with all your points. Especially this one. A defensive driving position (and also a racing position) is much closer to the wheel. You should be able to rest your wrists on the steering wheel when your back is all the way against the seat. Of course, to each their own. But, there are safer ways to drive that give you more control. I see these people driving with their finger tips and I pray they never have to swerve to avoid something...Also driving in a seating position with your arms stretched out is incorrect.
I second the point that there is plenty of room back there if this isn’t primarily a people mover. If you’re taking the kids to soccer practice a couple times a week and then commuting the rest, no problem. I have three kids in the back a couple times a week and they are fine for short trips. That includes fitting in one booster seat for the smallest, who needs it by law. They wouldn’t enjoy being crammed in there for an hour a day, 5 days a week, though.