I think its a great idea too. Or something like it would be a cool option. Just as you don't have to micromanage many things but can let governors do it, you could let the computer run your battles, or you try to get a little edge as an Emperor by being our own general.
That's great for the grand tactical level. But what about Strategic level war?
The grand strategic development game, city improvement, population growth, and researching is really on a different time scale than building units and moving them across the landscape to fight battles, even as grand tactical battles are on a different time scale from strategic warfighting.
(So you would have to make maintenance the main limiting factor in units, rather than manufacturing time, and you would have to make the AI able to handle that. Also you could have a "tooling up" factor, where you build a training camp for a particular unit, which is production consuming and requires a lot of maintenance, but once you have it you can produce the units at a good clip. Neither automatic unit production by a factory OR units being built over many years by regular city production.)