Interesting idea but I'm not sure how many takers you'd get as it kind of defeats the purpose of having a production system in the game. If you've got no control over what is produced it soon becomes irrelevant.
If you wanted to reflect some kind of political restrictions on your ability to wage war, such as is reflected here, then I'd be inclined to go down a different path.
Perhaps each HQ you create is attached to an individual city? Call the HQ after the city name. You'd be representing a federation of city states that have all joined together to defend themselves.
Each individual city raises it's own regiments (kind of like the American Civil War) but the catch is that they expect them to be around to defend their home city.
Every time you moved a particular HQ more than 3 hexes from it's home city you'd have to pay a political penalty, eg. say 5 or 10 PP a turn. You could move the individual units anywhere you want but they'd be operating outside of the influence of their parent HQ unless you called in enough political favours to allow them to move as well (you'd need a simple action card, 'call in a favour', cost 10 PP, for this to burn off the PP's).
To simplify it even further you could do away with the PP cost and action card and simply have a house rule that states that an HQ must immediately return to within 3 hexes of its own city once the enemy moves to within, say, 15 hexes of the city. That's where it has to stay, regardless, until the threat of enemy invasion is gone ( enemy > 15 hexes ).
You'd probably need another house rule to keep all HQ's at roughly the same level of troops to prevent yourself gaming the system.
Either way, you could still produce what you want but you'd be politically constrained as to how you fought the war which, I assume (?), is the effect that Lord Karg was after.