The Officers are a nice addition and appear to work well. Excellent artwork. Some feedback...
1. I'd agree that experience gain is awfully fast
2. I'd also agree that having the option to build a normal, non-officer HQ for 5 PP, as before, would be useful.
3. It'd be helpful if some information was forthcoming with regards to Max. Staff as it's an obtuse black box at present.
4. The Officer Pool is great but you are unable to see the stats of the new officers which makes any swap a wild guess.
5. The icon for accessing the Officer Pool could perhaps be made more obvious.
6. Perhaps it could be coded that the very first, default, officer that you get assigned to your supreme HQ could have a high Mx. Staff value instead of, what appears to be the usual, '25' value.
Other than the above, it's looking good.
And here's a suggestion, just 'cause it's Tuesday.
On the artwork for the officers (their pictures), you could plonk a small gold star down in a top corner. This wouldn't be for all Officers, only some (say 1 in 5), and would signify that they have been to 'Higher Command Staff College', or similiar.
The practical upshot of this is that only Staff Trained, gold starred, officers can command HQ's that have subordinate HQ's under them. You could easily (I think) code in a check for this when the player assigns his HQ to another - does it have an officer with a star? Nope? Can't be done.
The game effect of this would be a simple, but effective chain of command. Staff trained, gold starred, officers could benefit from your proposed 'logistical, command' action cards. They would also be valuable officers that you probably wouldn't want to risk in a front line command.
A secondary effect would be that you might be forced to put a less than optimum officer candidate in charge of a higher level HQ by virtue of the fact that he is the only staff trained one available. Kind of like real life when Colonel Outstanding can't get the job 'cause Colonel Blimp has seniority.
The first, default, assigned officer would have to be a gold starred one as he is in command of your SHQ. Any bog standard 5 PP HQ's without an officer would also be unable to act as higher HQ's which sounds about right.