Studebaker, and possibly other makers that had "suicide" rear doors, supplied a kit that consisted of parts that were installed in the posts between the front and rear doors that prevented the rear doors from being opened unless the front doors were opened first. The kit is still available from Studebaker parts suppliers. I plan to order the kit or fabricate my own duplicates of them for my car.
I was in a serious head-on car collision a couple of years ago when another driver crossed over and hit me. I now walk with a cane and found that I had difficulty getting into and out of the Bradley GTII car. Not so with the Studebaker sedan!