Something that could potentially make the bus slightly more fun and would cost next to nothing: theme each bus individually to some Disney property - ride, film, character, etc.
It doesn't have to be anything over-the-top or expensive, just something simple. Not a huge paint overlay on the exterior, but rather simple banner graphics above (in the slots normally reserved for ads for the next Beverly Hills Chihuahua movie, etc.). If they want to spend slightly more money, they could pipe in the soundtrack from the film or ride while you're traveling from place to place. Each bus would have its own unique identity, rather than its current theme of "generic infrastructure."
Each bus you get on the trip would have a different theme, and you could look forward to guessing what you might get next. One could be a Haunted Mansion bus, another could be a Winnie the Pooh bus, and so on and so forth. Imagine riding on the Space Mountain bus, with a star field overhead and the music from the Star Tunnel playing quietly in the background.
Think how much fun it is to guess what monorail color you're going to get next. Or what animal you'll get on the tail of your Frontier Airlines plane. I think it would be kinda fun.
Fantastic idea! It's so simple too. That is to say, the idea isn't rocket science, and wouldn't take years to figure out. I hope they do something like this. They did the tronorail, imagine a tron-bus!