I have seen people ask in the past for rules for DYO scenarios rather than the historical situations. The file is CCN Point Buy.
Up until now, the only things I've seen is the Variation Point Buy rules. Those were very good, but sort of limited both by the set (don't cover expansions) and scope (only generates a few types of force pool with limited customization).
So, I decided to create a set of rules to generate scenarios in a competitive environment. The included rules cover map generation, force construction, deployment, and victory conditions for various sized battles (from Small to Huge).
The force construction should do a good job of enforcing somewhat balanced and historical forces while still allowing a large degree of customization.
These rules have been playtested fairly extensively but I'm very open to feedback for continued improvement. If you grab the rules and play them, please take a moment to let me know what aspects you did or did not like.