I think knowing the exact outcome of every offensive action would take a lot away from game play. I enjoy taking my best available option based on the numbers and then having to react to the outcome. I think a formula where you know exactly how many hits you need would get boring.
Long range stun is a great idea, makes the arc rifle and engineer more useful. I also thought the Electro pulse could cause less damage but 100% temporary stun(1-2 rounds) for non robo enemies.
Is there a way to have soldiers going to a mission in their own country to receive bonuses? It would add extra strategy in selecting the crew that goes out on a mission. Maybe a balance to the aim and will perks could be that XCOM soldiers receive less XP for missions they complete at home.