Ys, you are purporting that every “non-Chabad Rov” is ignorant of a befairush Gemara in Sanhedrin (98b), with Rashi there distinctly explaining the possibility.
I simply don’t accept what you said for it being motzi Shem ra on all of Daas Torah.
Furthermore, the Abarbanel, Yeshuos Meshicho and Sidai Chemed explicitly cite that Sugya as a source allowing for Mashiach coming min hamasim.
So I simply do not accept that Daas Torah forgot a klur Sugya or would contradict the highly regarded Chachamim who explained it so plainly as to be unmistakenly applicable to Mashiach, whoever he is.
Also note that the Rebbe concluded his first Maamar with “vehu yigalainu” in reference to his father-in-law, the Previous Rebbe, already after his petira.
And to go so far as to claim “Emuna problems” and ch”vSh disregard a fellow Yid as a result is to be mechadesh Torah shelo keHalacha for which one loses their Chelek in Olam Haba. So that’s an ironic boomerang in that anyone who does so has earned by their code the very same treatment they relegated to another. Talk about “haposel bachaveiro bemumo posel”.
And make no mistake: it is not even a “fringe opinion”, but rather a bluntly clear Gemara saying in the simplest terms that Mashiach might come min hamasim, and the Rashi there clarifies it further by taking it further into the clear meaning of the Gemara, indicating that it is definitely saying possibly so!
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Sanhedrin Daf Tzadik Yes Amud Bais:
אמר רב אי מן חייא הוא כגון רבינו הקדוש אי מן מתיא הוא כגון דניאל איש חמודות
Rav says, if [Mashiach] is from the living he would be like Rabbainu HaKadosh, and if [Mashiach] is from the dead he would be like Daniel Ish Chamudos.
Note: without making even the slightest of adjustments to the implication of Rav’s statement, what he is quoted as saying is obvious. That Mashiach can come from the living or the dead. It is to avoid this obvious meaning that slight adjustments would be introduced. Rashi however makes adjustments in both directions and expands it to introduce two additional implications, one of which is presented as his preferred expansion, and even further solidifies the statement as allowing for Mashiach min hamasim.
Rashi says:
אם משיח מאותן שחיים עכשיו ודאי היינו רבינו הקדוש דסובל תחלואים וחסיד גמור הוה כדאמרינן בבבא מציעא (דף פה.)
ואם היה מאותן שמתו כבר היה דניאל איש חמודות שנדון ביסורין ב אריות וחסיד גמור היה והאי כגון לאו דווקא
ל”א כגון רבינו הקדוש כלומר אם יש דוגמתו בחיים היינו רבינו הקדוש ואם דוגמא הוא למתים היינו כגון דניאל איש חמודות
…if [Mashiach] was from those who have died already he was Daniel Ish Chamudos who was judged with affliction in the lion’s den and he was fully pious. And in this meaning, “he would be like” is not necessarily applied (i.e. either like, or literally)…
Rashi then goes on to offer another expansion, that Mashiach is being compared to a living or dead personality.
Note that the plain meaning of Rav’s statement lands squarely in between the primary and secondary expansions of Rashi, and persists as the original statement.
And again, the later Chachamim simply cite Rav’s statement at its face value, as indicating simply that Mashiach can fcome from the dead and be someone [else, who is] like Daniel Ish Chamudos.
But it cannot be stressed enough that Rav’s statement, without adjustments, actually says “if he is from the dead … he is like …”, and Rashi draws this out to the point of demonstrating that, yes, “if Mashiach is from the dead…”.
It’s in no way a hard Gemara. And with Rashi there are three take aways, Rav’s plain statement as is, Rashi’s first introduction further reinforcing the plain implication of the Gemara, and a *secondary* explanation that keeps the living Mashiach prominent. (Arguably because Mashiach will come from both the living and maybe also the dead. I.e. He will live and be known, and die, and then return for more.)
In conclusion I would argue that during the life of Mashiach, the characteristics of R”HK are seen in him, and after his death the characteristics of Daniel Ish Chamudos are seen in him.
E.g. if the Rebbe, when he was living he was mostly seen holding Rabbinic court; now he is more and more being seen in a different light from other aspects, such as every President inaugurating his birthday, or just recently every sitting US Governor getting together in one room to celebrate his birthday one year. ..just an example of how he can be seen in his life one way and differently now. Also as his Shluchim continually proliferate and grow in leadership/prominence and wisdom it affects the perspective of him. Bringing this into limited examples doesn’t do the point justice. Certainly now each person themself can maybe perceive in different ways how now we might see that back then he was unflinching in a proverbial lion’s den, whether spiritually facing some group issuing a cherem, or physically in danger of political assasination like so many lehavdil other radical social and political leaders were met with…
…and this is only a sample..
Another approach is that his personification in Techiya would be in a similar likeness to Daniel Ish Chamudos.