Before I get into it, I have no idea if this, or something like it, has been suggested before on the boards/forums (haven't really seen anything on OCE) or reddit. Please keep that in mind. Also, fair warning, long post (no TLDR).
I think everyone (at least, everyone who isn't a troll) will agree that Ranked is a strictly competitive mode, and should be taken with paramount seriousness and moderation. It's that very nature of ranked that is why I rarely, if ever, touch it. Quite simply, it's not an environment I find fun, and I play for fun (I'm sure there are many who have different views). However, that does not mean I don't understand the importance that ranked holds for a very substantial portion of the player-base, and it is that understanding that should allow everyone to view this suggestion with the same seriousness as they would expect from the queue itself.
With that said, I think everyone here will agree that there are certain individuals (whether few or many in number) that prey upon the innate seriousness of the queue for their *personal* enjoyment, an act that causes discomfort, disruption, frustration and rage in other players. It is exactly this that such players are seeking, for the individuals they are matched with to suffer while they have the time of their life making it that way. As a result of being exposed to these behaviours, there are many players who "break" from their self-control and resort to responding to such individuals in kind. Troll the troll, flame the flamer, harass the harasser, an eye for an eye. This is certainly not an environment and "culture" that can be maintained and addressed without serious attention.
Obviously, there are already systems in place to deal with undesirable behaviour within the community, *however* it would seem there is little, if any, room in those systems to address the ranked community itself, which some believe has become a breeding ground for the worst of the undesirables. All the time, positive and benign players are introduced to the Ranked queue, whether because of another player, or their own choice. While there are no statistics to work off, if even one of those players becomes a negative influence, that's one too many.
And so, that brings me to my suggestion:
The basic idea is simple. Whenever a player is punished for unacceptable behaviours, not only do they receive a standard punishment (chat restrictions, low priority queues, temporary/permanent bans etc), they receive a ranked restriction. A period of time during which the ranked queue is *completely* locked to them, which will persist for the duration of the punishment itself, and a time after. Such a system may be seen to "encourage" toxicity in non-ranked queues, *however* it can be said that such negative behaviours have a lesser effect in non-ranked queues, compared to ranked queues. Referring to one of my earlier statements, it can also be said that the innate nature of the Ranked modes attracts those with the intent to ruin games, and by "cutting them off" from such modes, there is a higher possibility of reform (which Riot has stated is the purpose of the punishment systems) or, at least, leaving LoL, and becoming some other developer's problem (sucks for them, but good for us).
Having explained what Ranked Restrictions are and some potential impacts on the game/community, I'd like to now suggest how they would be applied to each tier of punishment currently employed by Riot (this list is what I *personally* think would be effective, it does not necessarily represent how they would be applied if such a system were implemented):
Dodger penalty, 2+ dodges (30 minute queue cooldown) = 1 game Ranked Restriction
5 minute LPQ = 5 games + 1 week Ranked Restriction
10 minute LPQ = 5 games + 2 weeks Ranked Restriction
20 minute LPQ = 5 games + 4 weeks Ranked Restriction
10 game chat restriction = 10 games + 1 week Ranked Restriction
25 game chat restriction = 25 games + 2 weeks Ranked Restriction
2 week ban = 2 month Ranked Restriction
I realise that the chances of Riot taking any suggestion into consideration, let alone seriously discussing it's viability, is probably non-existent, but, at the very least, the players can discuss it in all seriousness. So, discuss.