As much as I agree that this would be nice… It would also be horrible. As soon as you do that, you’d have so many people selecting “I don’t want to be a back-filler”, that games with leavers would nearly never be back-filled, and it would lead to a higher amount of bad games than there are right now.
Honestly, I just think CMM needs harsher penalties for repeat leavers and possibly a small amount of “hassle compensation” for those who become back-fillers. This could just be a small amount of exp, or maybe a slight credit boost from the match, in order to offset the queueing time and the short amount of time played, due to being a back-fill.