Lucasfilm Story Group is responsible for that mess. They've been dismantled.
The ride is automatically down two hours of the day more than other attractions for SCHEDULED downtime. How in the world could that not sound right to you?
Thanks for the diagram. I can give you a basic outline with this. So, the new Coco overlay would have you welcomed to Dia de los Muertos celebration at the loading dock, with a "radio program" quietly playing about De La Cruz playing as you round the volcano. F is the first scene that features Miguel playing in his attic. This is followed by screens of Miguel feuding with is grandmother, and then of him playing De la Cruz' guitar. A fog screen with projected marigold petals flowing downward is used to transport guests into the land of the muertos. H is Miguel meeting Victor, followed by a large budget "Poco Loco" scene. The only thing kept is a repurposed use of divers on a cliff scene, which is largely a gesture to the ride's past. The ride skips then to Miguel meeting De La Cruz and finding out the truth in L. Boats then travel through a door which opens into Coco with Miguel, remembering Victor and singing Recuerdame together. Passing through another door, the rest of the former finale is used for Miguel's family celebrating Dia de los Muertos with all the deceased family gathered together. The boats finish by passing by Dante. As boats prepare to unload, a new radio station show is playing about the music of Victor Rivera with a new rendition of Recuerdame recorded just for the ride.
This is the proposed Epcot version. The CA version has two more scenes proposed, but uses mostly the same animatronics and props.
As good as something can look before it is green lit. It will likely come in after Mary Poppins.
I've heard a walk-thru faux veterinary care center is the most likely addition. The big draw would be coming face to face with a massive Toruk animatronic at the end. Other animatronics would be on display as well (under the guise of humans caring for the fauna of Pandora), but the Toruk is where the big money would go.
If that door doesn't close, it's a big no-no. The fact that it's happening on a regular basis enough to be in multiple videos, shows you just how much they're letting slide to keep the ride going.