Less ruined games!

What if, someone left. They ruin 4 other peoples' games right? Lets just say, a Rengar left a match, if he has positive kda and is not feeding, then if someone picked Rengar in teambuilder solo-q. They have an option to join that match that the other Rengar left. Then when the new Rengar joins the match, it will no longer be a 4v5. Rengar does teambuilder solo-q, other Rengar leaves, Rengar gets an option, Rengar joins, everyone is happy!