My stupid suggestion to fix the leaver problem in competitive:

What if, in the play menu, there was a little bar under competitive that said "backfill". And if you selected it, you could backfill into any competitive game with leavers and take their spot.

Here's the catch: winning or losing the game wouldn't effect your SR. That way you could practice playing in a competitive environment, with proper composition and people taking the game seriously (unlike current quickplay). It WOULD however effect the SR of everyone else on your team, the people who were there to start with.

This isn't a 100% flawless solution, but it gives teams with leavers a fighting chance instead of just accepting a loss.

Obviously leaver penalties would still apply to the people that left the competitive game early.

EDIT: After some replies, I realize now that a vote kick system could be implemented to prevent trolling. If all 5 team members agree to kick then that person gets replaced by another backfill. But honestly, I have more faith in the overwatch community than that.

EDIT 2: Just to clarify, I don't think he backflips rank should be effected because it would be totally unfair to fill into a game that's already 99% lost and have that effect your skill rating.