These systems are all good for your general Basic Roleplaying Army Battle, but Since this army battle is so big for the story, I figured I needed something that'd allow a clear view of how the army the PC's are affiliated with is affected by their actions, and as well a clear view of what damage the PC's have done to the enemy troops through scouting missions and sabotage.
One thing that came to my mind was to build an army like a character, where the HP is like Morale points, and when an army is out of morale, it shatters and is defeated. For skills, there could be different kinds of troops, with higher percentage the bigger the power of the unit. Say for an example, one side has 30 mutant liondruids, who are sswift and strong, so they have an Attack percentage of 2-3% per soldier, while they're not very tough and wear light armor, so they get only 0,5% per soldier in deffence, rounded up. Put this all together, and you have one "Skill" unit that attacks for 90% and defends for 15%, against another troop who, say, attacks for 12% and defends for 76%, first the attacking side rolls for attack, and the defending side for defence, then you somehow calculate losses between the groups, and then the defending side rolls for attack, and the attacking side for defence, and repeat the procedure.
Is this making any sense? Do you people have any brilliant ideas to help me out here?