[qqwref]

No, it actually isn't better, in any way. I thought my second paragraph was clear enough, but here goes again: having an exponential system like that would make it basically impossible to play a song that you get more than about 20 boos on, which would make FFR a lot less fun, and would also make it much harder to improve at FFR without playing some other game (such as SM). And luck would start to play a huge component in the game, because a single extra boo could completely ruin an otherwise acceptable score. Basically, yes, it would get rid of mashing, but it would also completely ruin normal playing, except on songs that you are already capable of getting very few boos on.

If you want to fix people mashing, you need a system that doesn't reward it, while still allowing normal play. And my favorite one is to just remove combo scoring, and give a full combo bonus no matter what, so that only PA matters.