Balancing the game in the future through Ranked Teambuilder

With well over 100 champions, League's roster is growing fast. Balance is going to continue to be an issue as the meta changes. I was thinking about how riot could control this a little better in the future and then I remembered that ranked Teambuilder is in the works.

Already each champion is labeled in different roles (fighter, support, etc.). What if champions are only playable in one or two roles in Teambuilder? Assuming that people join teambuilder based on role (Top, Jungle, Mid, Marksman, Support) rather than champion (as it works currently), players that sign up for the Support slot, for example, can only choose from the roster of available Support-tagged champions. Players who queue up for the top lane in Teambuilder would only be able to choose from the roster of top lane champs.

Some champs would have more than one role available (Yasuo mid/top, Quinn marksman/top, Lulu top/support, etc.). This would make balancing champions easier because items could be developed that only players who queued up as Support could buy, for example.

Downsides

• off-role picks wouldn't be allowed (no Bard mid, no Annie jungle, no Voli mid, etc.). This is the big one and would be a huge change from the wide-open format of the game right now, where any champ can go in any lane in any position.
• some champs work in a variety of lanes so they lose some flexibility
• would undoubtedly cause all sorts of rage and justifiably so because lots of people love playing their off-role picks (I've taken J4 to midlane, I'm guilty too)
• are Corki/Varus midlaners or marksmen only? Lots of strategies, such as dual ADC, that teams currently use might not be viable under a strict lane/champ regime unless champs are tagged, which might not always be the case
• swapping picks: not sure how this would out, but I'm sure there's a way to make it work. This is also a big downside.

Upsides

• easier to balance new items for specific roles without worrying about bleeding into other roles (like when midlaners used to build the AP jungle item back in S4)
• easier to balance smaller groups of champs against each other (30-ish possible tops vs 100-ish possible tops)
• opens up new design avenues for items and champs
• prevents some troll picks, especially when people sign up to play a lane but take something else (Support player taking Draven)
• would allow riot to change and/or buff champs that have fallen off the radar pick-wise (Elise, Yorick, Poppy, etc according to Lolking)

Please don't flame, this is just an idea I've been thinking about for a while regarding the future of the game and balancing such a huge number of champions. I'm probably missing some important factors so please let me know. :)