You also have to consider the bad that would go with this system as well and can it prevent that bad behavior from repeating itself.
I am not talking about bad gameplay skills but also mentality of a player for being S, A, B, and etc.
Never forget that back in early 2.X era that people did use PF to create learning parties but the issue of people with "better" skills ignoring players new to the old contents grew out of control because they felt their time was only worth using with other players who cleared the content and are skilled enough to burn through the content fast. It was not until the Punishment for quiting a DF run early and Bonus for helping new players were introduced that it died down a bit but that did not elimiate the issue completely as people found ways to get around the punishment through requesting being Vote Kicked or just holding the entire group hostage in the dungeon with them until they are Vote kicked or someone Leaved themselves so they don't have to face the Punishment.
A middle ground will be required to prevent such mentality from taking over S and A rank player base or else we faced with this issue once more where people are left behind because they could not meet "expectations" nor perform task the way a certain player within S and/or A rank would have done things just because they're new to the content even though their skills are atleast at A rank, B rank, or C rank.
A worse case scenario this system may promote groups of S/A rank players to look down on B Rank or C rank players and have these B Rank or lower players "Kicked" from the group in hopes of getting another "S/A" Rank Player or the entire group or one of the S/A Rank player quits the Dungeon because they did not get a full group of S/A Rank players.