Going back on topic to the type 9s... Looking at the concept drawings, it doesn't look like they are addressing the issue with the center truck on the type 8s. It looks like they are going to use the same stub axle design on the center section with the type 9s.
Thinking about it, I drew up a little sketch on microsoft paint.
If they put a ramp in the middle section (to accomodate people who can't do stairs) so that the midle section isn't low floor, they could probably put a full idler truck in there. The current typ 8s have the seats elevated on the middle section. The elevated part where the footrest area is is only about 6-8 inches above the floor. That would mean that the ramp would only need to be that high, which wouldn't make for a very steep ramp.
I have two ideas. The first one is a simple gradual ramp that goes up, then back down.
NOTE: Sketches are not drawn to scale. These designs may or may not work depending on the actual height and how much room they have to work with on the ends.
If theres enough room for a ramp that isn't too steep for a wheelchair to gp up, then this design would also work
Since the middle truck won't be powered, it shouldn't take up much more room than the current design of the center section of the type 8s. The ceiling height may be an issue though.
With the ramps, they would probably have to use rubber with the floor on the ramps so that people don't slip on it when wet.
Or, if possible, a single gradual curved ramp with a flatter center point also work instead of having two ramps.