Instead of using markdown, which actually is just another extension. I've made this extension use the native xlst template rendering, so it shows content no matter what other extensions are enabled.
I've made some progress on getting uploaded files shown based on your own configuration (adding a template to the mimetype + upload adapter settings), but this does not yet add the preview during writing/composing.
Totte I can't change the "upload" permission for any other group than "global".
I wasn't sure how to implement this, recently I found out how to do this properly so I will add this feature soon too.