As one without much knowledge of the disabled cycling community, just having seen this topic on the main page, I would have two questions:
1) are there particular disabilities in significant enough numbers that one style of accessible cycle would suit them? Whenever I have seen adaptive cycles in the past, they generally seem very customized to the individual, I would worry about how to stock bikes if one needed multiple different styles to accommodate different disabilities.
2) are there provisions for transporting the individuals off-bike mobility devices? Something like a cane probably isn't that difficult to transport, bringing along a wheelchair while you are on the bike more problematic.
Glad to see Detroit taking a lead in it, though!