I guess it would be awesome if you play Civ for the combat.
TBH, I play Civ for the math. You can literally calculate your likelihood of victory, quantify your combat success rates, and most of your victory is based on your ability to plan, rather than your ability to engage. If I wanted to play RTS, Starcraft is still on my shelf and Warcraft III box is right next to Civ IV.
I think the P-i-P screens would be a greater burden on an already processor burdening game. Really, I would prefer a graphics upgrade over a new "combat" feature. The implications for an AI that can out maneuver you when you have the odds are just staggering. The AI already cheats, they already get the micromanage advantage, and this is just one more tool in the toolbox that can ruin a perfectly victory condition because the AI launches a surprise attack and I really don't enjoy the idea of managing a real-time battle punctuating a long periods of planning.
The current military in Civ IV is intended as a tool, a means to an end, rather than an activity. The activity is winning the game. Military units are there to make sure that happens (or does not happen).