These are excellent points.The artillery-firing issue bugs me a lot - I frequently instruct an arty unit to target an enemy arty unit , but it instead targets an infantry unit close by. But since that doesn't happen all the time, I don't know what the default arty instruction is.
I would add my request that in addition to seeing total number of men in a unit, we also see that unit's relative strength vs. other similar units. For example, the Iron Brigade's high morale/training appears to give it greater strength than other units of similar size; the various sharpshooter units, and the Gamble's/Devin's skirmishers, should be rated relatively high in fighting strength (despite their small unit size) due to their being equipped with highly accurate and/or rapid-fire, breech-loading rifles.
RE relative-strength for artillery units, shouldn't their being equipped with 12- vs. 6-lb Napoleons, 3" ordnance rifles, or Whitworths have some effect that we should know about (greater relative strength, longer/shorter range, etc)?
Another request is one I've seen others ask for: the ability to dismount cavalry units. It would make them a lot more effective in fighting against infantry.