As far as the memory thing goes... I think it pertains specifically to forgetting who the WoLs were. We have Echo vision of the leaders' memories, from their souls, towards the end of Carteneau, and it even somehow includes Lahabrea monologuing. No idea why it occurred, but whatever did cause it was very specific in its memory loss. Rather similar to a certain clock mechanism used recently in Endwalker.
As far as red ball goes... I think that's right. I haven't paid attention in World of Darkness in a long time.
Zot/Babil vs. Ark - There's currently a visual connection and somewhat of a boss connection from Savage in Pandaemonium for Ancients -> Mhach.
Spoilers for Boss connection.
Hesperos in Savage turns into a monster resembling Diabolos.
There's a Cessair/Cait Sith reference in Elpis, too. They may be similar due to having their architecture passed down as the scary prison for monsters architecture via Ancient Memory inheritance. That's theory, but I swear to you every time I fight Erichtonios it feels like I'm in Dun Scaith. It could be that Fandaniel either intentionally or unintentionally had the towers manifest that way. I'm rather curious as to what summoning ritual was employed to was able to scatter Varis's limbs into them.