I don't really want huge THEME changes, just a 21st century ride: Here is what I'd like:
(1) queue music stays the same to start but the queue's appearance changes. Make it look more like we are passing through the corridors of a space station like at Disneyland. As we progress further, the lighting will get colder and colder and a soft version of the ride's new theme song becomes increasingly audible.
(2) The main loading area would still have an open ceiling but we would update the lighting to 21st century quality with no normal lights and a slightly creepy blue-light look giving everything a glow. No return for Crazy Larry, we are going for a more serious tone than that. Gone would be flying cookies and stars to be replaced with much more effective fiber optic stars that will now be the only thing above guests in the queue (and the only major source of light inside the ride building--no more stars poorly projected onto the ride structure making it too bright). Place one-way glass on top of the queue area to make the guests feel as though they are still inside a space station with a view of the stars (this also prevents light pollution into the ride area the other way).
(3) ride starts as usual, but now with on-board audio telling guests to prepare for launch as the trains pass through the first tunnels toward the large lift-hill, now given the really cool look of Disneyland's main lift hill, themed as a launch tube that rotates around the guests. Guests are given a countdown as they move slowly up this tunnel (now silently like Everest--no more clicketty-clankety) as the music builds to a crescendo, the entire rotating tunnel around us turns red with flames as we launch from about 0 to 30 mph quickly to the top, over a little bunny hop at the top where we would get strong airtime as we enter the zero-G of space. Note that this new section of the ride will necessitate that trains from both tracks now leave at the same moment, allowing the added excitement now of launching with another rocket of guests. The train would immediately enter a break-run at the top (otherwise the ride would be going too fast for the current track) before continuing.
(4) Added special effects along the ride course would, of course, borrow from all of our friend Space Mountains. I love the supernova effect at Space Mountain Mission 2 in Paris and the finale at Disneyland's ride is a really cool effect where you feel for a second like you are going backwards.
(5) For the Exit, follow Disneyland's lead. Take out the tacky displays, the tacky cameras, and the tacky moving walkways. Those aren't the way of the future and they break too much, I'm sorry friends. America is over-weight. Stairs are the way of the future. Retheme with metal grate stairs to make guests feel like they are still in a futuristic space station (read: effective lighting), with the exit themed as more corridors on the space station. Exit into a rethemed Starcade with gift shop and on-ride photo.
(6) I like the new lighting show on Disneyland's Mountain at night. Get it. Play the new ride's theme song in the plaza outside of the ride's entrance.