Not getting punished by someone else leaving

We have all had it happen, 5 minutes into a ranked game, mid laner gets ganked and leaves the game. What now? Your 5 minutes in and cant remake. Well rip 15lp. But i think i have a solution, what if when a person leaves the game in a ranked match and stays gone for a certain amount of time say 3 minutes, their team is marked. If the marked team wins 4v5 the hallelujah +15lp but if the marked team loses they lose no lp and the winners get their +15lp. I can easily see how this system can be exploited, but the other team opposing the people who exploit it wont lose anything for it. I just think this is a solid system and if you have thoughts or notice a flaw, please share. Im just tired of losing lp because some elses burritos are ready. Rito plz fix.