First of all, I've read pretty much 60% of your (Lyte's) posts in this thread, especially the last half, and I have a question before you start the new thread. (Or perhaps include it in the faq?)
Have you or the development team considered "role checks?" It would be similar to how WoW does dungeon queue, when you enter the queue, it asks what roles you'd be comfortable doing, such as support, carry, mage, tank, basically most of the roles already listed in the champions profiles in the LoL client. You can only select a role if you have a champion that fits it; especially now that free-play rotation champs are gone from ranked. All roles would default to selected if the player has a champion for that role.
I know that you answered many, many questions on the idea of what I shall refer to as "role stigma", especially in regards to making a player select a role. I'm not saying that this system force any player to play any role at any time, only that the random team of appropriate Elo rating will always have the (here's the keyword) ability to form a complete team. It still relies on player behavior and humans being humans, but it makes sure to prevent those odd times where you really have nothing to bring to a team because of bans/picks/pick order. The cost would be easily calculated, at least, as a coded flash screen and the backend needed to support filtering of matchmaking (although I suspect a similar system is already in place here.) This, imo, will balance out fluke wins and losses, encourage team play and diversification, and make the Elo rating more confident.
After having said all that, please realize I have only watched ranked play and the like, I'm not a ranked player myself yet. Perhaps this system could be used for normals as well, though?
-And a question unrelated to elo/ranked/comp play really, but what, if any, are Riots plans to make ranked more appealing (not to say they aren't already) to people say, like me, who watch live streams, recorded games, oogle over guides and such, but is too much of a chicken to click ranked?
(Edit: In retrospect, I see a downside of people only selecting AD carries or whatever they want to play, which could be both good and bad. If player interest is equally spread [I bet it isn't] then que times would be unchanged, I suspect a good many hate support though!
Perhaps instead of a selection, or even a screen the player sees, there is merely a filter for which class is "available" to that player, ie. what he has a reasonable chance to play as? To get into even more complex numbers here, since you know the ban ratios for all classes in the game, you could set that number+1 as a minimum to be flagged for that class. For example, throwing numbers out there, let's say 3 ad carries get banned on average in a game, if the player has 4 ad carries owned, his flag for that role would be set to "on". To get even more complicated, you could base this on how often each champ is banned on average in ranked play, and use that to get a weighted calculation. For example, say Graves is banned 65% of the time, then he would count as 65% less toward that number required. [A note: you can set an average here, so champs that are banned less count more toward the required total.] Obviously these numbers are much smaller, but you get the general idea. And finally, to completely complicate it, you could base these values on banned listings for Elo ranges, ie. banned percentages for 1200-1300 Elo ranking and the like. Complicated stuff, but since the player doesn't really ever need to see it, it doesn't have to be too simple.)
Warning: I made this post at 3 a.m., it's likely to not make much sense. ;D