Dave,
Thank you for sharing that link to our forum, I've been thinking of a similar approach as you and having a dedicated micropub.blog running on a subdomain for the same purpose once I set up my Write.As as a part of that domain in some way as well, probably on another subdomain.
Looking at https://tiny.write.as/asteroidal makes me want to integrate directly into site navigation someday, especially if I can customize the CSS to fit my journal's aesthetic.
Anyway I'll read the links you shared!