Is there a purpose to occupying on open tile? I see you can occupy the tile and set up a sort of "camp" outside of your city. I had hoped that you could travel to a distant place, set up a camp, and then operate out of that camp while attacking monsters/etc. and your march would just return to this camp when the battle was over. The couple of times I've attempted this however, once the battle is over the march just returns to the main city. It would be nice if the march would return to the camp and allow you to make multiple attacks out of that camp.

Also, what about the possibility of setting up subordinate cities as a "camp" that you can march from?
-or-
If your subordinate city armies can "port" to your main city for a march, could you port from your main city to a subordinate city for a march? This part could be beneficial in alliance wars and such as well.

Just a couple of suggestions, unless these are already there and I'm doing it wrong.