Was reading the thread for governors, and thought:
Hey, why stop there? Why not have a court of NPCs who provide bonuses? As the NPC succeeds at tasks, they gain XP and gradually their bonuses increase. It would be great if we had options to promote them from governors (maybe with a regional level in between), but then I like complexity.
Oh, and a system where instead of everyone reaches L2 at the same time, maybe a few 'sergeants' get promoted first, then move on up in the ranks to become unit leaders. When we make a 'stack', we pick one to be an army leader. Then we promote one of those guys to our military advisors.
No clue where science/magic advisors would come from, since there isn't info yet on exactly how that works. Honestly, I see research as being very much the sort of thing where the 'scientific genius' (necromantic genius?) leads a team of researchers (whom you have to train) to produce your technologies. Want the giant steam-suit to fight giants on their own terms? You may have to give up military training to produce all those engineers...
Diplomacy and espionage I can see both being done by 'hero' units. You pick your diplomat, assign guards, and send him forth with his orders. Although when Henry the Treacherous gets turned away from Not-That-Stupid-ville for having 200 pegasus knights and 300 bearback archers as an 'honor guard', you've really got nobody to blame but yourself... And spies I can see just filtering into cities quietly, with caravans, occasionally pesting you with 'requests'. Of course, you can set your Spymaster to 'approve requests of less than X value', or 'take no heads'.
But anyway, my MAIN point was figuring out if there would be a place for non-combat heroes, or whether I needed to mod that in.