It's not a bad suggestion per se. I just don't think that's what BB is aiming for.
it's not like it'd completely change or revolutionalize the game...
and even if BB developers don't want you to be able to choose your players hours that accurately...you could have 4 settings...50% 75% 100% or coach's choice...
and 75% wouldn't be right on 75% but more somewhere between 70-80%