The issue is you are working on uninformed assumptions and not experience. If, after a year or so of lessons and actual playing experience this turned out to be a real issue, then going about solving would make sense. While people are generally taller now, tall people have been around for hundreds of years. With instruments as old as the 'cello and double bass this would have come up by now. As I have said, the right endpin is generally the solution for both instruments.