Sorn28 If the idea you recommended was implemented, it could be abused in the following manner:
Player (A) pays players (B) and (C). What for? Players (B) and (C) have made multiple smurfs that they can play with player (A) on. Whenever player (A) is losing a match, players (B) and (C) leave. Players (B) and (C) will keep leaving ranked games unless they win, which will result in player (A) ranking up. This is just one of many ways your presented system could become greatly abused.
Of course, one could say "then why not make it harder to create smurfs - say, increase the amount of required unranked games?" And to that, I tell you:
This would quickly help the game die by turning off any new players looking to get into comp within a reasonable amount of time, and that regardless, any dedicated smurf will sail the seven seas to finish the job (especially if they're being paid to boost).