Interesting theory but aren’t all the dead gods already back? WotC basically reconned everything they messed up in 4e by bringing back almost everything in 5e.
A lot of gods died long before the Spellplague during the Time of Troubles (the events that led up to BG1 and 2). Bhaal was killed. Mystra was killed and passed his mantle on to Midnight. Cyric killed a whole
bunch of gods and took their portfolios, many of which then got taken back off him and shared out (Myrkul's got handed off to Kelemvor, for example). Lolth escaped the Time of Troubles by killing
herself, but instead of having kids with mortals like Bhaal did she just had lots of spiderlings who she kept in her nest the whole time until one of them emerged the survivor and became the new Lolth.
Not to mention that the Githyanki city is
built on the corpse of a dead god in the Astral Plane.
That said, it doesn't make much sense for the Illithid to be trying to resurrect gods.
Ilsensine is their patron deity and they don't even recognise
it as a divine power, more as... the perfect ideal to which they aspire.
They are known for venerating their children however - the hatching pools are one of their most closely guarded sites, and having one on a roving ship is rather unlikely.
My personal theory is that the ship was a research vessel and the tadpoles aboard it were the only survivors of the project that hadn't been seeded yet. A project to create illithid sleeper agents who could gather information from the surfacers, telepathically relaying it back to their kin in the underdark, much the same as Ilsensine plumbs the minds of surfacers from its nest in the Caverns of Thought.
