I'd also like to clarify where I'm arguing from on this. My day job is with the Michigan Suburbs Alliance, and I've been working on this legislation in that role for the past year and change.
If that were the interest I were representing here, though, the above would look much different: in that role, having Washtenaw in the RTA would be a much lower priority--not no priority, but I could consider it a pretty unqualified win even if Washtenaw were left out.
It's as an Ypsilanti resident, planning commissioner, and transit advocate that I think Washtenaw's exclusion is completely the wrong choice: every other avenue we have for creating the regional transit connections that Ypsilanti (and Ann Arbor) desperately need is busily failing us. (Else, "where's my train?" to quote every Ypsi real estate professional I talk to.) Considering this ongoing failure of our existing tools, I'd hate to see us throw away an admittedly imperfect opportunity to try a new approach.