It would still be possible to create 1 Charisma characters and use them in PvP exactly the same. And, it will still be done. It will just make it more difficult for those characters in PvE.
I think that all of us play this game because of interaction with other players. If someone dont want to interact, it is better to play singleplayer.
The PvP fights is the main reason for many players to play this game. At this moment, the PvP is only existing entertaining multiplayer fight occasion in the wasteland. So if you dont want that player will leave this game, just dont make any measures, which will be threat for PvP, respectively for entertaining parts of the game.
If you want be succesfull at PvP, you must have best chars, with best equip, best organization,... . All of theese needs to spent time. Your measure will add time demands to level up your char. But there will be always players, which will spent that time in that way, so there will be always pure PvP chars, but other players, which dont have enough time, will be unable to face them.
I think that the idea of this suggestion was to add disadvantage to pure PvP chars because you think, they are so overpowered. From my point of view, the effect of this change will be oposite of that idea, because less player will try to get best possible chars, so they will be naturaly unsuccesfull in PvP against them.