I agree with your very, very, very least part that units like workers and GP and spaceship parts should be able to occupy the same tile, but to totally bin 1 UPT military units would be to take away the best part of Civ 5. If that makes Civ 5 less empire management and more tactical war game then so be it. The expansion may add enough depth to satisfy us in those other non-war areas, we'll see.
I find 1UPT wars to be much more rewarding than stacks, and it's the funnest part of the game for me. I suppose it's important to play at the difficulty level that pushes you, if you're not losing units and cities some of the time then it's probably not that much fun. The AI can only cosnampete with strong human play via extra numbers, that's the reality and it's not the optimal situation, but I still find wars to be a lot of fun.