This is borrowing slightly from Civilization: Call to Power, but I think that the best solution to this debate is armies. Instead of dozens of units fighting 1 vs 1 battles across an entire continent, units are stacked into armies and moved together like traditional stacks of doom. However, when one army attacks another, the map zooms in to a closer, more detailed battlefield map much like in Call to Power, with terrain matching the hex of the defending army. On the battlefield map, combat would proceed much like it does in Civ5 with 1UP and ranged units. Battles would still be turn-based (but still conclude within one overall game turn) and conclude when one side loses all of its units or retreats to the edge of the map. Having units fight in armies would also alleviate the enormous traffic jams that Civ5 wars turn into. Anyway, I feel that this combat mechanic would more accurately capture what real warfare is like than Civ5 or previous iterations of the game.