I'm surprised at the civility in this forum *SHOCK*.

That said, to weigh in with my official answer I've gotten through interaction with various people at various different levels of BL Publishing: The Star Child *HAS* to exist for Rhanda Dandra to occur. The Thorian Ressurection, Emperor Reborn, and "Divine Vessel" was invented by Gav Thrope since he absolutely detested the name Star Child. Mr. Simon Spurrier also brought back the idea in Xenology.

As for the Sensei... it is heavily hinted that MacLeor, McLeod, or whatever his name his (All these Scottish and Irish Immortals look the same to me ) who serves as the Emperor's right hand is in fact his bastard Sensei son in the first Horus Heresy limited edition audiobook.

Basically, all of these things are concepts that GW doesn't speak of, yet exist. Also, the entire Star Child lore spoils the ending of the *ENTIRE* game universe, so that doesn't exactly help marketing much...

As for Squat, there have been numerous attempts to bring them back. The abort project of the Demiurg were once such attempt. "The Tyranids ate them" started as a joke by the developers. Sadly, it seems the initial fanbase didn't get the joke and, when enough people believed in it, they made it official. Zoats are now a hive fleet that was utterly decimated as of the last incarnation of the Tyranid Codex.