What I think is the biggest problem with league

"There are normals for that" You know where MMR is very "balanced," where people try their best because it is just "normals," where people won't flame you for losing.

So you're saying that you should just be free to randomly test something that you don't will work in the exact environment when 4 other people are counting on you to play to your utmost best with your best chance of reliability?

What do you want the system to do? If you do end up winning despite testing something in a ranked environment, you get rewarded. If you don't, then you face the consequences of your actions.