So in other words, you don't want any supports on your team? Once you figure in the brief games that end in 20-minute surrenders, even a carry might be hard-pressed to average that 133 CS/game (assuming a 50/50 win rate; even HIGHER if one wins more than 50% of the time)
And if you're a pro support? You'll average a CS of like 20-30 per game at most. That means at least 26,000 games played to rack up 80k CS.
Also, win count is a bit over-stated, as even the worst player will eventually win, and hence, eventually even the worst player could get 300 normal wins.
My suggestion is a suggestion; an idea; a starting point, I'm sure it would need refinement, but to clarify it: a player to start ranked (in addition to the current requirements) would need to either have bronze or better in one of their profile badges, allowing shooting stars to start sooner, or they would need to have 300 wins, so that eventually anybody could enter ranked games.
Adding some modest requirements is not a bad idea, but on some level, ranked play is still a learning experience for everyone, and everyone needs to remember that. If you can't help your teammates win, technically you don't deserve the win, even if you get it.