On the top left of the main screen is a list of units/stacks. Method to quickly see if stack has movement left in current turn, without moving to actual unit, and clicking. This could be a tiny icon added to the unit/stack box on top left of screen. Red for no movement, green for full movement, yellow for partial movement. (or does yellow mean speed up? <jk)
EDIT: almost forgot, how about a way, when city growth (pick a free upgrade building) to make the pop up window translucent so you can see whats under it? Prefer previous idea posted above that this popup window allow either 1) put off acting on it until later in turn, 2) allow immediate access to appropriate city screen and then, upon signal from user, return to pop-up screen to choose the building.