I was looking at the code to fortify/airlift new units built in a city and had some ideas I'd like to run by you. I was going to implement them when merging with BULL, but if you're interested in these I'd rather help to get them into your mod directly as I've looked at the places where the calls should happen.
You set a rally point for cities by selecting them and shift-clicking on the desired rally point. We could extend this by adding
- CONTROL - Fortify when rally point reached
- ALT - Airlift to rally point
- BOTH - Airlift to rally point and fortify
ALT would obviously only work for city target plots, but this would allow you to set up an airlift-and-fortify rally point with a single click.
We can even change the color or shape of the rally point ring: red means go to and fortify, bracketed square means airlift, and red square means airlift-and-fortify. CONTROL + SHIFT + CLICK on the same city would clear the rally point as usual but also set the fortify-on-build flag.
I feel the immediate visual feedback will make using this method easier to use and remember than key combinations. Those could be left in of course for toggling without having to set the rally point again.
The rally point setting is in CvCity::doTask() which receives bool values for the keyboard modifiers. The plot drawing code is in CvGame::updateColoredPlots() and a pretty simple change. Even if you don't want to add the mouse behavior, I recommend changing the icons on the map for selected cities.
Edit: Oh yeah, and the last piece is that we could add an icon above the city bar indicating if there is a rally point and the fortify/airlift states. A flag would make a good rally point icon with something to indicate that the unit fortifies when it arrives. A parachute could mark cities that airlift new units. Actually, the fortify upon arrival setting probably isn't needed on the map; the hover would work well for that.