Can I make some suggestions on this scenario?
More often than not, the campaign is over after the first two years because either the Spanish run out space to retreat (if the French are played by the human player) or the French are destroyed piecemeal (if the Spanish are played by the human player). May I suggest some changes/additions?
The French army rarely lost whole divisions in the fighting in the Peninsula and rapidly substituted units or brought them up to strength (except in the later stages of the conflict when France itself was invaded by the allies post Liepzig). Therefore I suggest that French brigades/regiments (only) should be reconstituted if they are eliminated in battle, from the mass of replacements that a French player accumulates over time. Italian and German contingents should not be able to reconstitute though because they were one off "offerings" of co-operation from allies. Obviously generals who die should not be replacable. This would allow the French to be able to recover somewhat and provide a challenge to the human player even if the AI suffers a catastrophic defeat. It would prolong the game and make it more challenging.
Each French army conducted operations indipendently from their bretheren within the Peninsula. Marmont at Salamanca (for example) was leading 6 divisions and Massena's invasion of Portugal consisted of a similarly sized force. Maybe they could be given army headquarters so that they could really operate indipendently.
One small adjustment that could be done concerns the Convention of Cintra event. More often than not, the Army of Portugal is either eliminated or manages to escape. If the army is destroyed, these generals are normally injured and then returned to service. If the army survives, the generals survive as well. This creates a problem since Delaborde and Thouventot return when the army of Portugal is reconstituted. Is it possible that once the Convention of Cintra event is activated, Delaborde and Thouventot are removed from the gameplay and return once the army of Portugal is reconstituted? It would be a bit similar to when Bessiers or Dorcenne return
to the Peninsula.
On the Spanish side, a few more regular replacements tied to the Spanish Insurruction event would go a long way in improving their performance in the field. Also prior to the reformation of the Spanish army in 1810, the Provincial militias (the guys in white and red) should be classed as militias and draw replacements from the militia pool. This would rapidly bring up to strength the Spanish formations and provide the French with a more challenging foe. When combined, these two adjustments would allow the player to accumulate some regular replacements over time to be able to sustain war over a long time.
Also is it possible to adjust a bit the promotion system for the Spanish? Minor successes over the French normally resulted in immediate promotion. Maybe an easing of the promotion system vis-a-vis the Spanish could mimick this situation.
Sorry for being a pain in the neck but I have to admit that the Spanish campaign is a big time favourite of mine.