A "triumph rework" suggestion

What if, instead of giving a certain % hp to champions upon kills, Triumph actually healed you according to the damage you would have dealt if your target didn't die

(I know it's not really clear, here's an explanation. Your spell hits for 500 damage, and your target has 200hp. You'll kill it, dealing 200 damage, and healing yourself by 300 hp)

I know it would probably fuck up execute spells (like R dealing 9999999999999999 true damage, or R with a ridiculous scaling if executing), but it would be more fair and rewarding. I'm taking for example ARAM, tanks are unkillable during teamfights due to triumph, because they keep healing and healing for a % hp, and when they have 5k hp, erm you get the idea

Or even during laning phase, Triumph actually allows (the now long gone) botlane marksmen to stay in lane if they killed their opponent, allowing snowball.