I think "x number of wins" is really arbitrary, though I do understand your point.
Even if you went with 500 wins, each win won't signify an actual increase in understanding or skill with the game. I started playing League in Season 2, but only played unranked blind pick 3's with a buddy who introduced me to the game. We were so awful.
Eventually we thought we were good and switched to 5's. It was a whole new game. I didn't even know what I should be doing even though I had briefly read up on Summoner's Rift. I took a break from League because I was frustrated and discouraged.
I came back just before the big Season 3 changes hit. I did a lot of research on champs, playstyle, laning strategies, warding, jungling, and started watching streams with explanations of what they were doing. That's what made me better. An interest in learning.
I only have 99 wins this season, and 113 losses. And to be honest, I learn a lot more from the losses than the wins. It's really hard to replicate something that worked in a win. It's much easier to fix the problems and mistakes you made in a loss.
What I'm trying to say with this short novel is that I don't think a number of wins will fix much. The only thing that would truly change the game would be if everyone put in time to really learn from mistakes and learn how to improve, rather than just mindlessly queuing and hoping for a win.
EDIT: Also, I think people providing constructive criticism would go a long way as well. Instead of calling your mid a noob because he's letting his laning opponent roam, remind him that he should either follow them, or push the tower instead of continuing to simply freeze the lane and last hit. Things like that. There's so much negativity thrown around after each mistake that it's hard for anyone to really learn what they did wrong.