I know I haven't commented on it as I have been focused on other topics (mainly my disappointment at them gutting a Garlemald expansion something many people have wanted for a while) but with my opinion on the Hydalyn/Zodiark debate is that they should have just gone with what was hinted at back in 5.2 and have it be that Azem was possibly looking in to dealing with the Final Days at its source or looking for a better solution hence why they remained neutral.
Have it be that they wanted to avoid any more bloodshed and saw neither option as truly solving the problem or sustainable in the long run as well (as well as having to choose between siding between their best friend or mentor) and so they began to look at the problem at its source. I would change Elpis to a memory sequence. This way there is no disastrous implementation of time travel and no Venat having knowledge of future events. Elidibus simply uses his power in the Crystal Tower to access memories that are burned into the soul or possibly use the Azem Cyrstal that Emet-Selch made in secret that may contain memories that are only accessible by Azem or more specifically their current incarnation. Have it be that Azem found out about what was causing the final days but before they could act on that data the battle between Hydalyn and Zodiark started and the sundering occurred. Now the player uses this knowledge to deal with what is causing the final days at its source.
There you go, no timey-whiney shenanigans, no Venat knowing key information and choosing not to act, the Hydalyn and Zodiark conflict is kept morally grey with no right or wrong answer. Oh and maybe just have it that the Metion came in contact with the Endsinger instead of being it and instead have the Endinger be a being similar to Nyx from Persona 3. This way the final boss is as everyone said more of this lovecraftian concept instead of a kawaii bird girl from Etheryies. Metion could instead be used by Azem to track the Endsinger to its source and now is used by the WoL to do the same.
And of course this goes without saying that this would be 7.0 so 6.0 can be the Garlemlad expansion and better wrap up loose ends.