It is a mitzvah to have priests and Levites included in the Great Sanhedrin... And if none can be found, it is permissible to have a court of exclusively Israelite judges. Rambam's Hil. Sanhedrin 2.2
If the judges are arranged on the seats according to their wisdom, how much wisdom is being a Kohen worth?
In other words, how much wisdom on a non-Kohen can be sacrificed in order to promote a Kohen into a Sanhedrin to fulfill this Mitzvah?