i'm sure its been suggested before but i think it would be great for ranked, you can do the role you want instead of having to fill in a role you might not be so good at and there won't be anyone picking champions to counter you like in draft mode, plus if there is someone missing from your ranked team you can just get a fill in of your choice!
Look, I'm going to be honest here:
People need a basic understanding of each and every role in order to know how they function within a team, and cooperate with each other. For instance, if you're an adc main then you should at least know how to support by proxy, what kind of supports there are, and how they do their job and you can help them do their job (because their job is helping you do your job, so it's fair).
Everytime I see this, I cringe:
"gg no ganks" -know different types of junglers, and that sometimes a jungler is going to gank a different lane because they know the jungler is elsewhere. Play your laning phase differently if you have a 
(you won't have much pre-6 pressure) rather than a 
(epic level 2-3 first bloods).
"It's a support's job to ward" -no, just stop
"Noob support ks'd me" -early game, supports' utility can be a bit stronger than an adc's weak attack damage. It's better off getting an assist and ahead of your enemy than your support backing off so you can last hit, only to find that they're outside your range. Just deal with it and farm.
"wtf y no group?" -certain toplaners scale better into late game as monster tanks (like Nasus), sometimes their teleport is on cd (walking to mid lane might take longer than the actual teamfight). I've seen so many teams try to force teamfights when they're behind, or they don't wait for their tank/bruisers to lead the charge.
Team builder, to me, leads to complacency. You're going to forget what certain roles do. Tanks are more than damage sponges, and supports are more than warding bots, and adc's don't deal a lot of damage early game, and mages and assassins have cooldowns and resources (yes, even Zed can run out of energy from time to time).
But, I'm going to say this too: this is my opinion. It is not fact, it is not truth, nor is it a lie or slander. It's just my opinion, so save the insults if you have any and lead an intelligent discussion. I see so much flaming and condescending behavior ("ur bad/ ur bronze") toward fellow players on these boards in the week I've been here over mere opinions, so let's keep it civil.
I think you should choose you're roles and what lane(s) you would like to play and then champ select like normal, keeping the counterpicking so things are slightly less luck defined.
Big Bang Bob has a great idea. Ranked Teambuilder would just be Ranked Blind Pick...
