There's a mod that does exactly that. But that only helps to a certain extent. It also leads to get more experience and better equipment and that's the actual problem. Player grow in strenght far more than enemies do, due to how equipmentm abilities and so on scale.
So after a certain point, a mod like that would make things actually easier, since you reach higher levels faster and get access to certain spells/equipment. Another mod to reduced XP gained somewhat helps, but doesn't really fix the core issue.
