Big idea: Use email/IMAP as the storage backend. Gives me arbitrary metadata (headers), text file in disk storage, universal tools. I can have posts in draft, if I hook up an SMTP server as well, I can have easy bot apis.
Using mime/mulipart I can store the original post, attached images, html rendering all together.
I'll need to import current posts, but I'm going to have to do that if I want to update my on disk format.
I'm probably going to need a second copy of dovecot/whatever IMAP server, I don't want to get my actual email mixed up with this stuff (except check out namespaces maybe?)