I could see Tiana and Naveen... maybe Louis as physical figures, but even as I think about it, the idea of characters just standing there blankly talking to the audience (as seen on Mermaid or Frozen) is just awkward.
For starters, you and I are simply going to have to agree to disagree with what constitutes as awkward, lesser or greater ride experiences. Provided those characters you listed are doing something that AA versions of themselves are capable of doing, I would like to see practical versions of themselves doing it. Like I've said, to me, nothing beats having the characters actually there, in reality, with you and I would die on that hill. It's why I think the practical figure shots of the T-Rex from the first Jurassic Park still look better today than the CGI shots of more recent films. Because it's actually there and we as an audience know it. If you disagree with that notion, then you and I will simply just need to shake hands and move along.
But Disney knows how to build good AAs and continues to do so to this day. -and they should, because Guests are paying a premium to experience their parks. They should get the premium experience. Sure, AAs are more expensive but ya know what? Disney is more expensive for them, too. Going above and beyond to make something worth their while I think is a good business practice, though it admittedly becomes more rare in all things as time goes on.
That isn't to say uncanny valley or awkward-ness can't be a thing. I guess it's largely up to your discretion. Do I think most of the static fish figures in Mermaid are awkwardly or poorly presented? Sure, I do. But figures like Ursula from that same attraction or Olaf from Frozen's, I think are great.
I don't know what Disney's intention in terms of storytelling is going to be with the Splash Mountain overlay but that will certainly factor into the execution of them. As
@norcal1219 pointed out, it will depend on whatever the storyline calls for. Splash's key character figures aren't the most advanced but they do what needs to be done in a way that's enjoyable (when they are working) and get the point across as the log travels past them.
-and if at some point, the storyline calls for the characters to be "standing there blankly" while talking to us, I fail to see how them doing so in person is any more awkward than them doing so via video screen. But that's just me. It's all in the execution. You have to remember that an attraction like Mermaid is meant to be directly presented to us as a story from Scuttle. In this way, it's sort of a "meta-book-report"-style ride because it's literally being book-reported to us. The AAs that fill the attraction and the way they interact (or don't) with us are a reflection of that. With current Splash, we're just sort of along for the ride passing by show scenes of events unfolding with the characters. If PatF does something similar, you may not have to worry about the AAs "standing there blankly" towards you because the figures will be off in their own world, having their own experiences as our ride happens around them.
Or maybe not. Maybe we'll be more directly involved. We'll see. In either case, me getting a thank you from a Tiana AA is preferable to her thanking me via video screen. Unless the storyline calls for her to constantly be changing back and forth between human and frog during that moment, which leads me to my next point:
... AA's are not a requirement for an attraction to be successful. Louis as an AA would either be incredibly expensive to produce, or never look as fluid and life-like as animation on a screen.
I'm not sure I follow the logic with "expensive" being used as a reason to deliver a lesser product or experience, especially when Disney has proven time and time again that they have no issue doing it. A Louis AA with trumpet in hand I really don't see being any more difficult to create than Ursula over in Little Mermaid.
But make no mistake, the way I worded my comments was intentional. My comments about "impossible" moments and "when possible" should be taken into account here. I agree that, in general, when something becomes an unrealistic possibility, other avenues should be looked into. For example, Louis singing, talking to Guests or otherwise doing things that the range of motion an AA can achieve, should be delivered to Guests with an AA figure because it creates a better ride experience. However, let's say a scene calls for Louis' tail to be bit by another gator, Louis to jump into the air screaming, hit his head on a bayou branch and then start tumbling down a waterfall. That is a perfect example of a time where using something like screens or projections are not only understandable and logistical but also pretty much the only possible option as the alternative AA route would be nearly impossible to build and otherwise maintain.
No one questions why, for example, Universal didn't build
actual, practical Transformers to transform in front of Guests and do the things they do on that attraction. Because that kind of tech doesn't exist and likely won't in our lifetimes. But if said tech was readily available and able to be both built and maintained at a price Universal knew was affordable, I would advocate for it over screens, in another lifetime.