I think it would be interesting to have a switch (checkbox) labeled diversity. If checked, a player would be allowed to build only 1 type of unit per turn at each factory. This would necessitate some special mods with more factories for some countries. It would be interesting to force people to build some units they don't normally build and learn how to take advantage of them.
values: only affects placement. the count is equal to the number of this unit allowed per territory, and the value is equal to "owned" (we are only counting units owned by each player), or "allied" (allied too), or "total" (which counts enemy units too)