The one unit per stack thing really shows it's flaws when you have lots of large civs fighting across a landmass though. The land can become 'clogged' with unit

The one unit per stack thing really shows it's flaws when you have lots of large civs fighting across a landmass though. The land can become 'clogged' with units to the point where it can be hard to move around properly. Couple that with Civ V having possibly the worst AI of any Civ game to date and it's a recipe for frustration in many cases. The AI civs would never use naval units properly and it made a large portion of the game easily expoitable. Civ 4 was the other extreme, where with many large civs you would end up with the 'stacks of doom' on a single tile containing dozens of units. Obviously this wasn't ideal either. Some sort of unit stacking limit would have worked I think. Some mods exist that allow you to stack between 2-5 units on a single tile in Civ 5 but I'm not sure how well they work or how the paltry AI copes with the change. Still, I always felt like stacking by combined arms would have been better, like a stack of 5 units limited to 2 inantry units, a cavalry or vehicle unit, a ranged unit and a siege weapon.