Based on what I've seen so far in the thread, here are my thoughts.
Right off the bat, I am going to say that I am
cautiously optimistic about the Princess and the Frog retheme to Splash Mountain. I like that PATF is getting the attention it deserves and I do think it's clever (in a way) that this ride is reclaiming the ride based on the rather antiquated (and frankly, racist) movie
Song of the South for themselves, you know? But Disney's track record with its ride rethemes is, well, polarizing (look at the Antman and the Wasp retheme for HKDL's Buzz Lightyear Astroblasters) so I really hope they invest a lot of time and cash developing the retheme so that losing Splash Mountain will be all worth it.
Anyway, going back to the prompt. I'm for the bayou retheming idea,
without the voodoo (I don't think we'd want to end up on another Twitter thread about racism in WDWMagic). From the looks of it, the facade of the ride seems to be set in the New Orleans Bayou (judging by overgrown landscape Tiana and Louis is in) and I think if we blend the surroundings in with that, it would work harmoniously with each other. I also think the Bayou is more familiar to everyday guests, especially for fans of the film (since you know, the majority of the movie is set in it). On the onset, I don't think we'll do any drastic rethemes (except for one; I'll get to that) if we go for it. The Hungry Bear restaurant is set on stilt posts over a portion of the Rivers of America, which seems to be a common feature
in houses in those parts. Harbour Galley could easily be rethemed from New England to New Orleans.*
Now, the Pooh Conundrum. Either way we go for the retheme, I think it would have to go and rethemed to something else. Ace's idea for an "airboat ride in the swamps" seems sound but given the "scenic placemaking and transitions" prompt, I think that should be the least of our worries. As long as we all agree that Pooh gets the boot, we'll be fine. Let's just say the new ride will be in Phase 2 and call it a day. Pooh can go over in Fantasyland and take over the Canal Boats (which by the way,
isn't a novel idea).
* Edited: removed this one "...and be expanded to table service by adding a riverboat in the dock and have guests dine there instead (I think
@AceAstro suggested this)."