No guests are allowed to sit on the floors. If they are and can be seen by the driver, the bus is not susposed to move. This is a large safety hazard. That being said, the driver cannot always see all guests, especially when the bus is full. Again, this is a case of parents needing to be responsible for thier children's safety.
The intent of the low floor busses is to allow wider aisles for handicap access. If you lower the upper handrails, you now create a safety hazard by having the rails in proximity to a guests head. I will say that there could be more hanging straps. This would help a guest who is of shorter statue. I don't feel that Disney should trade handicap accessability for the seating arrangement of the RTS. The wider aisles make it easier to disembark guests normally and in case of an emergency. The low floor bus is also the only one that works for certain types of mobility devices.
To return to the RTS style bus will make for longer load times, less overall guest safety, (although it provides lower handrails for shorter guests) less handicap accessability and longer overall transit times.
Last night a driver took a wrong turn leaving POP, corrected his mistake within 2 minutes, and had guests complain to a GSM about the fact that the trip took longer than it should. (The reason was because he was a newer driver and had just had trouble with guests not complying with the safety rules. He was still flustered from that incident and just turned out of POP wrong)
I'm sorry, but despite our best efforts, we can't please everyone!