How exactly would those proposed changes decrease toxicity? Looking at it, it only looks like, in a roundabout way, it would only just make more toxicity, if not doing nothing entirely.
So, let's follow your example here - someone queues up, gets autofilled to, say, Support. Well, nobody wants to play Support, and neither does the autofilled player - so, they dodge, and continue on into another match where they get autofilled again, with the other nine players still in queue, with one team lacking someone in the Support role.
Which means someone needs to fill that role, either someone who queued up as Support, or yet another unfortunate like the one who dodged who got autofilled.
So, now one person probably isn't going to play for a while (keeps getting autofilled, keeps dodging because of it), and several other players are going to have to deal with extended queue times (thanks to that one player cursed to be filled), and another team is probably going to have to deal with a bad set-up for their match because now the enemy knows who they're going to pick - and vice versa.
And this is only assuming that a player dodges due to not wanting the role they got. There's other types of queue dodgers, some who do it for better ends than to just not play a role. Some people will dodge to spare themselves and their teammates from a potential troll or feeder - and, with this proposal, those players are now dealing with extended queue times, potential penalties for queue dodging (if in Ranked), and they have to deal with autofill for doing an ostensibly bad thing.
Doesn't that seem a little unfair, to lump punishment on top of punishment on top of misfortune to one player who just wants to play an honest game?
And then, of course, your proposal runs into a particular problem: Because Autofill exists, there is Autofill Protection. How does your proposal handle this? Does Autofill Protection counter Queue Dodge Autofill? Or does it work the other way around?
Ultimately, I don't think this suggestion was thought through as well as it could be, and it really doesn't do anything to reduce toxicity - it looks like the only effect it'd have is to increase queue times and frustrate lots of people. And this is even ignoring the fact that it doesn't do anything about the "autofill as source of toxicity/aggression" point.
Beyond that, though (as Chermorg had discussed), it's not the game's systems/mechanics/elements that make players toxic, it's their own lack of restraint. Even I get frustrated in League, whether by getting Autofilled in weird ways or having to deal with other players, but I don't get toxic.
