“Yachid V’Rabim halacha K’rabim” “normative Halakhah”…
Myfriend, please find me a legitimate source which states that there exists such a concept with regard to gedolim who do not have real semicha and whose words are not upheld by a Beis Din of semuchin, or at least were not debated with the parties holding both opinions present. I do not believe you will. So while you may be correct regarding belief in mashiach (Actually I do not believe you are. The Chasam Sofer’s shitah over there is that belief in mashiach is not its own ikkar but rather simply comes from the ikkar of belief in the Torah and the nevi’im, as the Sefer Ha’ikkarim says, who disagrees with the Rambam, and according to him R’ Hillel wouldn’t be a kofer today either because he simply interpreted the navi that the mashiach spoken of had already come; but that’s not what I want to focus on now.) you cannot stretch that idea to a place where there is a machlokes rishonim.