Even having a choice of Front/Middle/Back when you buy your ticket could help solve most of these issues and as Thunder Bolt mentions most restricted view seats are identified at point of purchase.
The earliest ticket buyers get the best seats! No we can't let you have your preference of block/front/back/middle but you will get the best seats decided by?
Be better going back to sit/stand where you want then at least we won't have the 'sit down I can't see' or the 'you're sitting in my...