I did write rules for army men. It was really simple. It basically ripped off WH40K's AV System.
It uses D6s. Every model has three different values. Accuracy, Toughness, Wounds.
Accuracy represents the number on a D6 that you need to roll at or below. Things like moving or moving or shooting multiple shots reduces your accuracy.
Toughness represents how hard you are to wound. The higher the better. To wound someone, after a hit has been scored, you at a D6 roll to the strength of your weapon and try to equal or beat their toughness. If the target was in cover, then you have to beat their toughness.
Wounds are how many times you can be wounded before you die.
Everyone moves 6".
You can activate three of your models every turn.
There were more rules, but it pretty much worked for most toys.