"The intrepid heroes after their long fraught journey strike down the corrupted hivemind that has been pulling the strings all along. And as they rejoice the camera slowly pulls back from moonrise tower to reveal it is in fact a minature replica, as the camera pulls out further we see, indeed Moonrise Tower, Baldur's Gate, and all points between are but a exquisitely recreated replica within a child's bauble, a snow globe."
I'm on board but we can get crazy with anything if you question the very nature of existence.
How would all the forgotten gods fit in, and Gale's quest in particular.
I've been treating Netherese magic as an easy way for them to hand wave (literally) some inconvenient rules regarding magic in D&D but I can get behind something weirder
Dealing with your fears and pains plays very well in with the origin characters but what about Cust M. Char?
And how do the Gith fit in?
Oh yes, this is definitely questioning everything, but nothing so far gives me the idea that there is a clear plot.
It makes me feel like it's a plot for players, play with the past and possibly affect your relationships and strength of deities, maybe even strength of shadow or mystra/silvanus over Baldur's Gate?
I mean, the entire conflict between goblins and druids doesn't make sense; you can just go to Moonrise Towers on your own, once you, the player know it.
And obviously Minthara will never go fight the druids on her own, especially if this is some play on memory or possibly even changing past.
We don't even know, if we can actually safely become mindflayer. We could possibly be 'The Adversary', but what if we actually can't abuse the powers as much on full release?
What if we actually lose control of our character and die? If we knew that much, it would be clear. And I feel like the interviews with the devs are suggesting that...
I tried to be friendly with the Illithid and his thralls at the shipwreck. It didn't go well. They don't care for anything (well maybe Omeluum).
I think that we won't be able to get the tadpole out, ever. It's a DM plot to make us twitch and squirm.
What would it be like to have a tadpole in your head? Just keep thinking about tadpole in your head, that is your main problem, nothing else matters right?
And than imagine we don't RP a good cleric as good cleric we might face a very dark world outside, our god might not refresh spells, who knows...
It's a really cool concept imho, but I don't know how doable it even is.
I am not really sure how Gale fits in yet, I think his quests might have something to do with the history of Telamont Tanthul and Karsus though.
The Gith are clear ones - everyone bitched about this encounter, it's hard because it's supposed to be. You will likely have a big problem if you kill those Gith there. It might mean that you change the past and Gith are weaker, or else... No idea.
Gith are clear enemy of Mindflayers.
I wouldn't believe into Jander=Astarion ( or close to), because Jander is portrayed as a character of firmest morals, capable of stopping even the evilness of the undeath and not losing faith even in Ravenloft and Avernum; Astarion is a survivor, instead.
Other symbolism you've mentioned is too unstable as a theory for me personally, but interesting nonetheless (spiders and Minthara especially so).
You are completely right, it doesn't really fit the character. But people affected by shadowfell do go a bit insane... I think that there are some twisted story similarities there, even just based of wiki.
I don't even know which version of Jander would we be dealing with, but I do feel like Astarion's character is a mask and there is a lot more to him than a poem on his back in infernal.