It seems feasible to write a javascript plugin to directly publish a note to MicroBlog, with metadata being written in the front matter.
To do this, I believe I can combine the How to create your own Obsidian Plugin tutorial with an existing plugin and the micro.blog posting API documentation.
The first iteration could be relatively straightforward, storing an app token in the settings, and using the front matter to store: - publication state (draft, published) - url - preview
Then, a command palette actions could also be used to publish, like Fleeting Notes does it.
Updating, and photo/video upload support should come in a next iteration.