Rso,
Source: See Sefer Meiras Einayim 23:1 regarding the baal shem tov that there was none like him and he will be moshaich as well as Sefer Kerem Beis Yisroel in the name of the Shtefanisht Rebbe regarding his father the ruzhiner that we have merited techiyas hameisim will be the same day as moshiachs coming so his father will return as moshiach. These words were stamped as divrei kadosh by sadigura chassidim and still appear in their kovetzim from time to time. David Berger likewise acknowledged this in an email response to this source. to quote him “In the last two hundred years or so, with the relative decline of Christian threat, we find a handful of comments, primarly among chassidim, that entertain this possibility..” he likewise says “There is some reference to the possible return of King David”. There you have it from the horses mouth:There are sources for this. He just 1. doesnt think this is the majority opinion and 2. thinks that lubavitch adds parts which make it unacceptable. But one needs to separate various points being made at the same time. From here its clear even david berger acknowledges people have defended this.
2. I am not basing my choice on who was the greatest in the generation. I was arguing AGAINST someone else who wished to say that since there is yeridos hadoros the rebbe wouldnt be chosen since he is a yerida from previous dor. So i said by that logic you can only say the first option is the min hameisim option because anybody else isnt as great by that criteria. Obviously i disagree with that and it doesnt mesh with the gemara. I agree that that isnt how one should judge this
3. a few rabbanim here and there have suggested that in the past century. Id have to dig them up again. Will let you know. Point is, u could speculate whatever u want to be hashems cheshbon i doubt we know everything that goes into that decision. nistaros l’hashem
4. RoshYeshiva you are thinking of the sefer yechi hamelech hamoshiach, the second work. Yechi hamelech is just on rambam. but yes there is a sefer with haskamas which explains this.
5. Rso, you are missing the point to chezkas and being chosen. Whether its true or not this is whats often claimed(tho not always). So if this is what the main claim is then the attempted disproof that there are better candidates is a misplaced objection. Object that it isnt true ok, but one cant object there are better candidates if the whole argument is that this is no longer a matter of candidacy. That isnt a good retort to the belief. One has to bring arguments against what a person believes not what they dont believe.
Rso, be reasonable, this is not the proper format for producing various proofs of an entire case about how the rebbe fits rambam. Even if i could demonstrate that these things are mashama from the rebbes interpretations of rambam, u would just say the rebbe is wrong and you think pshat is instead like this because ur hergish says otherwise. Thats the whole problem, people give all kinds of interpretations of rambam, if u dont like the rebbes u will retreat into someone elses which better fits the way u think. seichel plays these games. The better place to start is is it possible to read rambam that way, are there sources for that way of learning rambam, can it be backed up in general and is it consistent? This is a more modest starting place. That there is A READING of MANY which would make the rebbe chezkas moshiach, The amount of reading and thinking it takes to go through sources with an emes and open mindset to the information and spend time thinking back and forth is more time than we have available here and i honestly dont believe anyone claiming to do it in a few hours between posts is being truthful with themselves that they are truly considering the points that would be made. Each criteria in rambam is its own world with various back and forth points and mekoros and svaras.