So lets say you find a way a to exclude bonus players from the PF, this still doesnt guarantee that the other players know what they are doing or that they are able to clear the run. A bad player that was carried once can easily lie to you and be bad. What happens then? How will you filter those players?
Removing bonus players is possible, but it wont fix the issue, at it best you will remove total clueless players from the group (which can be verified by asking them questions about the fight), at it worst you are putting a wall before newcomers who have skill and want to learn and improve these newcomers often do their best to prepare by reading guides.