This right here.
The college I went to, Rutgers, had a large bus system pretty much like WDW (in fact I think they both use the exact same bus model) and every bus stop has a digital display stating the estimated arrival times of each bus line. Were the arrival times always accurate? God, no! If you were at a stop after a student center the display would say the bus is arriving in 1 min and 20 minutes later it shows up, but that issue was because the drivers would take giants breaks at every student center everytime. Disney would probably have less of an issue with this considering I don't think would have tolerance for a driver to take a 20 minute smoke break every single time he pulled into Epcot. Rush hour also effected the times, but not as much as the drivers themselves. Overall though the system was a Godsend because you knew whether or not you had time to run and grab food at a Grease Truck next to the stop. There was also NextBus.com which you just can just log onto on your laptop or smart phone and check the arrival times as well as bring up a map that displays a selected route and the location of all the buses on that particular route. There was a way to get the times by text too.
This would be the best way imo to improve the system. No more not knowing if you have time to use the bathroom before the bus shows up. Taking care of that alone can make the bus trips a lot more bearable.
Here is the online bus locator for Rutgers if anyone wants to look:
http://www.nextbus.com/predictor/stopSelector.jsp?a=rutgers
Just keep in mind that its summer right now so its running very infrequently. Usually the buses run about 10 min apart from each other.