You sir, are the grand master! 
Works like a charm and I truly appreciate you sharing this.
I don’t know if something like this could be used by the developers of Obsidian to workaround the issues some people mentioned here. I’m not a developer myself, so whatever others were trying to explain on why Obsidian can’t open the .md files, goes over my head 100%.
Anyway, just wanted to thank you for sharing this 
The .md files now have a different icon based on the MarkdownHandler.app
I was able to change this by changing the .icns file inside the MarkdownHandler.app (Right click > Show Package Contents > Contents > Resources > AutomatorApplet.icns).
I delete that file and copied the one inside Obsidian.app and put it in that same Resources folder.
I kept the name “AutomatorApplet.icns” just in case, because I don’t know if that would make a difference or not.
And now all my files open using your script, and have the Obsidian icon:
