More shortcuts like selecting units fast with keyboard numbers would be nice. My suggestions:
-Backspace: When a stack that was moved before is selected, using backspace should cancel the latest step that stack did.
Words (They should be disabled by default, optionally turned on in personal settings)
-I: Auto buy infantries with all reinforcements from a city that's selected. If a whole country is selected, buy infantry in all its cities.
-Autobuys: T: Auto buy tanks, M: Militia, S: Marines, B: Bombers, etc.
F: Open/Close Finances screen
Shift: While it's pushed down don't show unit pop-ups.