1) Add a tech which allows the use of an additional device for a unit so we can make more unique combinations.
2) Does it make sense to have boats and planes stationed in a city at the time of attack perform at full effectiveness? I'm not sure if it doesn't but it seems counter intuitive for me. If ships are caught in port, are they as effective? Maybe we can assume planes in a city are patrolling overhead, nut should it receive the fortress bonus? That part doesn't make sense.
3) It would be nice if the change in resources were displayed in a tooltip when moving workers from one role to another. For example, if moving a farmer to a scientist the tooltip would display the amount of food lost and the amount of research gained when the farmer is hovered over the science work slot.
4) Have AI upgrade more of its early game units to improve tech. During the late game I'm still fighting a horde of low powered units.
5) Field training is kind of overpowered. It can work on so many units and it is easy to accumulate a bunch of those operations. A human player can easily make the effort to group their units into a stack for a massive army upgrade. I don;t think the AI takes advantage of this. Maybe either make the AI use this tactic or limit the field training to only 1 unit.
6) Allow the player to reorder the build queue by dragging an dropping the items.
7) As a faction performs more of research in 1 category (ex mathematics), give some type of bonus to the faction when researching that category.

9) Allow the player to queue up research. Yes, the user may want to change their mind once more techs are exposed, but it helps to remember what tech you are trying to get to. The player could always go back and change their mind once new techs get exposed.