I'm also want to see paint.net in the Windows Store. And if there is any interest maybe I can help
I have just published a desktop application in the Windows Store. Instead of using the Desktop App Converter I did everything manually. It's not hard to do this but it takes to time to get all details right. The result is a file contain a manifest, tiles, references to dependencies and all files that needs to be installed.
Now I think it should be quite easy to adapt this to paint.net. In principle, I just need to change some strings and change which files that needs to be in
