Measuring damage is an interesting suggestion but I don't think it will work. What if we say "no damage attacks mean you can't attack further" then they raise a no damage attack to a level 1 unit so a little damage is dealt. Then we raise that to anything under 10% damage means an attack lock out and they then send one reasonable unit to deal 10% damage.
The problem with this sort of thing is that any behavior that imitates in any way actual in game behavior you can't do much with.