Not if you discourage stacking (as opposed to banning it). You want a middle ground between "put all your units on one tile" and "you can only put one unit on a tile". I believe that middle ground can be achieved either through stacking penalties (loads of wargames use these, imagine a 10% strength penalty per unit after the first on the tile - two units sharing a tile are 10% worse, three units sharing are 20% worse etc) or through collateral damage (where units sharing a tile all get damaged or destroyed when one unit gets damaged - Civs 1,2 and 4 used flavours of these). Basically you want a system where you can get the job done by ramming 100 units down someone's throat if you have overwhelming production superiority, but the efficient way is to use only as many units as the terrain allows. That way production gives you an advantage, but using your army efficiently might let you defeat that advantage. That way you get the tactics side of the Civ 5 1UPT system, as well as some of the AI-comprehensibility and general usability of the Civ 4 stacking system. No worries.