I've mentioned it elsewhere (I think), but the only way to come to a middle ground between 1UPT, and stacks, is to get rid of tiles completely. Different units have a different zone of control. Cities have a zone of influence. The design becomes much harder, the concept is much harder to realize, and the game becomes less 'fun' and harder to handle for most - and it becomes 'not civ'. In the end, Civilization is not 'our game' to design. We, of course, can voice opinion, but in the end, a proper Civ player will adapt to the game the designers produce.