The idea is good, and graphics wise they could easily implement that without any major changes to the UI.
While the idea is nice, it's implementation seems more like fantasy.
The code behind, oh boy.
To put it simple. Let's looks at a no 2 options system but one option system where you only pick 1 role.
The system will simply make "virtual" teams with what people que.
So let's say we have
5 people que as top,
7 as mid
3 as junglers
And that's it.
you'd have 753 teams combinations.
each one of them waiting for 2 more spots. And the system has to find 2 of those teams also in mmr range of each other. For the sake of argument let's say every player above is in the same mmr range.
So, you have 105 teams out of just 15 players.
Now you add the second choice for everyone and the "teams" grow exponentially. 105*105 most likely.
11025 if I'm not that bad at math.
and if you add in more possible roles that number grows a bit to much to be managed..
which is why with out current technology, unless riot figures out a great match making system to lower said numbers is never going to happen.
Something like that doesn't come out of the blue.
even if I were payed 1 mil $ I might not be able to come with that system even if for the next 3 months I'd assemble a team and go math math math every day trying to come up with a good algorithm