Pretty good ideas. I have a few as well, some of which are similar... Please note that there may be spoilers for UP in my description of An UP Adventure...
The Great Movie Ride
I have two possible concepts for this. The first is a completely different attraction and the second, which I just came up with, is an updated version with a few new scenes and a new interactive element.
Idea 1: You enter the Chinese Theater as normal, but the giant screening room becomes the entrance to the Disney Film Institute. There will be two briefing rooms similar to Test Track or Tower of Terror. Inside, you will be briefed by the head of DFI (played by Robert Downey Jr.) on the latest in movie going technology: the ability to literally journey into movies. Guests would next enter the DFI Testing Facility to be the first people to try out their latest technology. The ride vehicle would be a modified version of the Dinosaur vehicle with two touch screens in each row. During the ride, guests are transported inside some classic Disney film moments such as flying on a magic carpet with Aladdin, coming face to face with Pete's Dragon, lightcycle racing from Tron and much more. Afterwards, guests will get to be in their own short film by answering a series of questions on the touch screens, then by reacting as the "director" tells them to during the filming. What guests experience during this section is based on the average of all votes from the touch screens. They can make everything from a sci-fi adventure to a pirate film. At the end, guests enter a screening room to see themselves in the film.
Idea 2: For the most part, the ride itself will remain the same as it's always been. There are a few changes I'd like to make though. Scenes from Alien, Tarzan and Fantasia will be completely scrapped. New scenes based on Tron, Star Wars and 20,000 Leagues Under The Sea will be added. A new film reel in the screening room will be done and it will be extpanded to add in some of the films that were not in the original, such as Wizard of Oz and Public Enemy as well as the three new additions. I'd also like to add in a new interactive element. In the screening room, guests will be greeted by Martin Scorsese who informs them that they will be featured extras in his latest film. During the ride, Scorsese's voice will be heard and he will give instructions to guests on how to react to certain scenes. Cameras will be placed throughout the entire ride and at the end in the large screening room, there will be a shortened montage of films, followed by the film shot using footage of the guests.
Pixar Place/Backlot Tour Area
The Backlot Tour area up to the HISTK Playplace will become part of Pixar Place. Several new attractions will be built in this area.
Monster's INC. Screamcoaster: Boo has been captured by Randall and it's up to Mike, Scully and you to save her. Board a flying door and fly through lots of heavily themed areas on your quest to rescue Boo! The ride would use an inverted coaster ride system. Each vehicle would seat four people, two on each side of the door. During the ride, guests will enter large doors that transport them everywhere from the Hemilaiahs to inside children's rooms. It would feature scripted sequences and short stops along the way, so it wouldn't be a pure rollercoaster.
An UP Adventure: Join Carl and Russell as they journey to South America in their flying house! Guests will board vehicles that look like couches with balloons attached. Each vehicle will seat two rows of up to 3 guests per row. The ride's storyline would begin when Carl is being forced to go to a retirement home near the beginning of the film and end after the final battle scene. I would like to incorporate several special effects such as clouds while the vehicles are flying above ground, smells from each area, advanced animatronics and really putting the guests into an animated world. I'd also like to see image capture incorporated so guests can see themselves as part of the world of Up.
A Bug's Life Playset: Children can enter the world of A Bug's Life by playing in a recreation of several areas from the film!
Radiator Springs Racers: A clone of the DCA ride would be added where the Backlot Tour currently is located. Movie props and such would be relocated to a different area of the studios.
I'd also like to see more Pixar themed resturaunts in Pixar Place, such as relocating Pizza Planet and perhaps making a Chef Gousto Table Service Resturaunt based on Ratatouille.
Sounds Dangerous
As mentioned above, I'd like to see this replaced with a Star Wars based sound show hosted by George Lucas. In it, guests would get to help create sound effects for a classic scene from one of the Star Wars films and then they can enter the sound labs for more sound based entertainment.
Indiana Jones Stunt Show
I know this show is a fan favorite, but I think it needs to go. It's replacement would be a new boat ride entitled Indiana Jones and the Lost City of Atlantis Adventure (IJatLCoAA for short). Guests will board a tour boat and enter the lost city hoping to find beauty and treasure, but end up finding an ancient curse that will trap them inside the sinking city forever! Indiana Jones comes to the rescue to save you from a watery fate! The ride would feature several drops, including a fairly steep backwards drop and a final plunge into the ocean depths.
Star Tours
Would be replaced with Star Tours Episode 2. In it, guests waiting to board a Star Tours vehicle are informed by General Akbar that they are to be sent on a covert mission to Hoth to get inside information on the Empire's plans. Cabin effects such as freezing and lazer damage will be encorperated into the current vehicles.
Voyage of the Little Mermaid
Since the new little mermaid attraction is apparently coming to Magic Kingdom, why not replace this with a new broadway style show? The first idea that comes to mind is a show based on Enchanted, but if you want to stick with an animated feature in this spot, how about one based on Mulan or Hercules?
Beauty and the Beast: Live on Stage
That show has been in this location forever and I think should be changed. In that location, an Enchanted show might be a better fit.
There are some of my ideas. Thoughts?