In Teshuvos V’Hanhagos (2:285) Rav Shternbuch writes that although it is a mitzvah to have meat at a Seudas Bris, if meat is very expensive then it is permissible not to have meat in order not to embarrass those who cannot afford to serve meat at their Bris. He justifies this aberration because he says that nowadays even Kings do not eat meat for breakfast and therefore it is not a Bizayon to the Seudas Mitzva to have non-meat menu. He also brings from the Eretz Chaim in the name of the Maharan Azulai that in certain countries there was a minhag to serve fish instead of meat at a morning Bris in order not embarrass those who could not afford meat.
Fast forward to his Teshuva 3:294 where Rav Shternbuch quotes his earlier Psak and questions it. The mitzva of Bris Milah is referred to by the word “Sason”. Sason, explains the Vilna Gaon means happiness expressed outwardly, as opposed to the word “Simcha” which means inward happiness; in the heart. This outward expression of happiness is manifested by a great banquet in honor of the mitzva and therefore he says, one should be Makpid to serve meat at a Bris. This he says is the opinion of the Maharsham as well as the Brisker Rav.
Rav Shternbuch in his sensitivity to those who cannot afford to pay for a “Fleishig” Bris, recommends inviting fewer people but not compromising on the menu.