OK, this took some time, but I now finished to read through the complete discussion and to take some notes while doing so. You can find the attempt of a summary in this gist - I hope that the content won't hurt anyone's feelings and that it doesn't have gross omissions. And while writing that: my sincere respect to the work done here, and not only to the technical work but also to that most civil discussion - starting from opposing ends in places and working to a common approach with no friction, that's impressive.

In case the notes might be useful, please reply with corrections and/or a proposal where to best post them; if not, no harm done - writing them down already helped me.

Two more questions:

a) If I didn't miss it, the option to use Racket's types or contracts has not been mentioned when discussing the potential formats of type signatures. Not only are both syntaxes field tested, but even if Racket is no longer Racket Scheme, it should still be possible to "steal" some of Racket's definitions for the purpose discussed here.

b) Any concrete item where I can support now? Time is limited as for anyone, but for any concrete task I can at least check whether I would be able to help. Otherwise I'll go through the repo and check for options based on the current status.