Shlomo, I didn’t see in his first question a doubt or inquiry regarding the nature of bias hamoshiach; rather, he asked how it can be considered an ikkar if it’s a “machlokes”. I answered that we see this by Miriam, so there’s precedent for ikkarim to be subject to halachik jurisprudence. That’s not saying “it’s a halacha”, it’s saying that it’s not static and that can be evidenced by its halachik development.
Re, kuzari; I don’t see how your points on the kuzari and the issue of how there can be machlokes regarding ikkarim are related to the OP’s original assertion that believing without derisha vechakira is “childish” and my response to him, which was demonstrating the soundness of mesorah based emunah without drishah vechakira.
But to answer the issues raised:
We don’t find a machlokes in the rishonim regarding the veracity of the ikkarim. Contrary to what some sensationalist bloggers and zoologists claim, we don’t have any rishonim on record who believe in corporealism. Nor do we have any who say that Hashem isn’t omniscient, omnipotent, above time/space, or finite. The rest of the ikkarim are the same. The only machlokes is about the need for ikkarim (just believe in the Torah!), The definition of an ikkar, and so on.
In terms of the mesorah, this can be analogous to how most halachos that are based on drashos are universally accepted, while the pasuk or s’vara that they are derived from are debated (this is how the ohr somayach explains most machlok’sim). There can also arise questions as to which halachos are deoraysoh and which are derabonon, asmachtos, etc..
Sevara is deoraysoh. The rishonim who held of deriving hashkofos from philosophy believed this to be Torah in itself (when Torah logic and exegesis are used, which is part of why the rambam says to first learn torah and then go into philosophy. The same way the conclusions we derive from our own lomdus are true and misinai(kol ma shetalmid vasik asid lechadesh….), Hashkofos are as well. M’idach gisa, the bartenura on moshe kibel torah misinai aays that pirkei avos begins with the shalsheles of mesorah in order to stress that hashkofos and mussar aren’t something chazal determined on their own, the way chachmei umos haolam do, but rather is part of moshe kibel torah misinai. Based on this, the rishonim definitely had a mesorah for hashkofa (which would explain that they agree to all the ikkarim), while machlokes can arise in areas that may have not been as vital, like whether hashgocha protis applies to animals, and other very abstract concepts.