The book of the dead gods mentions that severaly names on the last page have been stricken, the last three completely. I assume that the last three are the dead three. As their names are not in alphabetical order the book uses a different system of grouping. Can we assume that all of the gods on that page were connected? That would indicate that some of the others are part of the complot. I guess pretty much every god floating in the astral plane could be brought back somehow. What is in it for the illithids is one of the big questions. If they had indeed lost the nautiloid designs and someone helped them to build new ones that would be worth a great deal for them. No nautiloids, no astral empire. The gith must be very alarmed by the prospect. There really should be a dialogue option to tell the Gith with the dragon about the mindflayer vision of a nautiloid invasion. A few dozen red dragons would certainly help to keep the illithids at bay.
I sometimes use thought experiments. I don't necessarily believe in every idea I post for discussion on this forum