If a Minhag has developed as a Siyag Ve-Geder to correct some michshol, and that Siyag Ve-Geder was effected by a Chacham and then it was ratified by being popularly adopted as the Minhag (i.e. the Minhag did not evolve from a Machlokes in Halacha but from some weakness in Mitvah performance) then a new Chacham may not nullify that Minhag (see Teshuvos HaRosh 55:10 and Igros Moshe OH V.3, siman 64 and Igros Moshe YD V.1, siman 13).
So once a stringent minhag is established (based on a geder — i.e. separate seating at weddings) it can never be revoked, based upon the above?