Many people especially on page 1 say it wouldn't work out but I feel since all parties have a common enemy there could be a potential golden end.
I mean... Byleth literally sides with every side throughout the Routes and agrees with all of them if he chooses to. You, as the player, do so as well, technically. It's totally possible to sympathize with all Routes isn't it? I didn't find that hard at all. And therefore personally I came to the conclusion: If noone is objectively in the wrong here then it's also possible for everyone to agree on that.
First of all: What does Rhea want?
One could think as head of the Church of Seiros she wants the Church to continue existing and therefore this is incompatible with Edelgards goals.
In game Rhea rarely referred to the Nobility in a way that makes me believe she wants the nobility to stay no matter what though.
All in all I feel like Rhea just wants to 'revive' Sothis. She'd go really far with that. What if she just gets her back? What if that reborn Sothis just tells her that the Nobility has to go?
So what I could see happening is:
We get a Route that focusses on Those who slither in the Dark. Even before Edelgard starts a war something happens that makes everyone aware of TWSITD's existence and their plans.
That makes even Edelgard reconsider her initial plans.
Basically a 'common enemy' scenario. While that route progresses Byleth would have a different connection to Sothis. Don't know what makes the most sense tbf. Maybe they fuse normally but Sothis then awakens even more so that Byleth even remembers Sothis' life which essentially makes Byleth a reborn Sothis. Or maybe they don't fuse at all and Sothis starts remembering by herself.
Whatever it is - after THSITD have been dealt with there'd be Byleth and all three houses and the church. With Byleth practically confirmed to be Sothis reborn he could just unite them all because let's be real whichever Route we choose before in the end everyone was licking Byleth's boots anyways.
If the reborn mother of Rhea tells her that the Nobility has to go, then Rhea won't oppose.
With the Nobility gone, Edelgard has no reason to delete the church. Furthermore Edelgard didn't even struck me as 'opposed to Religion' so even she would acknowledge Byleth as a reborn Goddess.
The other two houses weren't that keen on upholding the Nobility as it is before 3H either.
Dimitris Grudge against Edelgard can also be dismissed by blaming TWSITD instead because you know, they were the ones responsible for Duscur anyways (I kinda forgot... was that ever confirmed somewhere or just hinted at? whatever it was - it didn't make really sense to blame Edelgard as mainly responsible anyways.)
I wasn't happy with that clash anyways. He's like "why did you do the things you did in Duscur?" and Edelgards like "well I haven't done it" and yeah he just didn't believe her. I felt this was just a poor way to establish a conflict. She's not with TWSITD. It's despicable that she's cooperating with them to a degree but if that kinda doesn't happen because of a golden route then I don't see why this couldn't be solved.
And now after I wrote all this: No, I don't want this either. If that ever happens I won't be having a problem with it though.
