I don't even get the point entirely. Since when was solo queue ranking ever supposed to be a reflection of how good a player is at a particular position? What is this 'splash' mechanic (does it not defeat the purpose of position ranks to begin with?) Why are we trying to complicate things at all?
Back in the day you had a number and that number determined how you would be matched against other players. The number was called your elo and your ranking was determined by what range of elo you happened to be in.
If you won games your elo went up, if you lost games, your elo went down. It was simple and it worked.
The number actually showed how good a player was at winning games of league of legends relative to other players.
At some point we moved to the weird division/promotion system (still have no idea why) wherein people reach their goal of plat 5 or diamond 5 or whatever and then just get stuck there because they dont have the motivation to reach for masters+, but they wont get demoted out because it's basically impossible to get demoted down a division these days.
And although I wasn't a fan, that was fine. Then we moved on to selecting our positions before the games, which probably solved a lot of trolling that would happen in champ select when people didn't get the roles they wanted. Atleast in lower ranges of elo.
And that solution was mostly fine except that it: now created an enforced meta of 2 people bot 1 person top 1 mid and 1 jungle AND it had to be band-aided with autofill.
And now because of the autofill problem we are trying ANOTHER band-aid solution aka position ranks. And things are going to get a LOT more complicated.
One of the first problems with position ranks is that if I'm a player who only cares about my rating for 2 positions, what motivation would i have to even bother trying when i get autofilled into the other 3? Well, apparently the solution to this is to make your offrole rating somehow affect your main role rating. AKA DEFEATING THE WHOLE POINT.
And can that 'splash' mechanic not be completely abused by someone who for example climbs to d1 on their main role and then just plays offroles to increase the rating of their mainrole artificially by beating up gold-plat kids?
And then you have the 'tightening mmr' for people who swap roles? Well guess what, that tightening mmr shit is going to take so LONG in season where people maybe play 100-500 games on average. It's just not going to work.
My prediction considering all of this? Position ranking is going to fail worse than getting rid of solo/duo. They're only rolling it out in na/kr because honestly, i think they know this already.