Thanks again. I did think of that, but it takes a while to replace all the factors. I was after something a little quicker...
Hm. Before doing that, I'd probably ask over in
this wonderful thread, located within the modding subforum. Modders would probably know the answer to your question, or at least know if there's a faster way.
Edit: You can probably set all instances of 'general = yes' to 'general = no', and change other factors that affect rebel strength (like unit composition; getting rid of all the cav/cannons and just replacing them with 1.0 infantry composition, for example, or maybe even 1.0 cavalry so they take tactics penalties too). Probably turn instances of 'reinforcing = yes' to 'reinforcing = no' as well.
Edit2: Honestly, that last one sounds like a good idea, considering rebels that reinforce pull manpower from an unlimited manpower pool, meaning that them sieging down provinces has no impact on them, as they get to straight ignore attrition.