There will be three main Stat, Health, Skill, and Focus.
Health deals with anything concerning the body such as defense, strength, regeneration, and power.
Skill will deal will dexterity, speed, agility, technical proficiency, and well, how skillful one is.
Focus on the other hand, would pertain to concentration, senses, control, mental fortitude, and the like.
Let's take Rem's ability for example, the Bomu Bomu no Mi.
Bomb Fist [Health] - An explosive punch. Literally.
Bomb Cannon [Healthx2] - The explosive power of Rem's punch is cannon-like in strength.
Bomb Gatling [Health + Skill] - Rem delivers a barrage of exploding punches.
Bomb Gatling [Health + Skill] - Rem delivers a barrage of exploding punches.
So from Rem's technique list, he'd have a total of 2 Health and 1 Skill. In terms of Technique damage, Bomb Fist would do 1 damage while the other two would deal 2 damage. But if their target has a defensive technique such as Thick Fat [Health], which has 1 point in Health, then Bomb Fist would deal 0 damage and the other two techniques would only do 1 damage.
If it's too complicated of a system, I can come up with a more detailed on in like 4 to 5 hours.