samtp - I think you're looking for the answer to two or more problems here.
- Can I trust that a plugin is (relatively) secure?
- Can I trust that the plugin will be maintained?
- Can I trust that the plugin will be good quality and work as described?
So far EmDash has an answer to what I think is the most important question (IMO). Can I trust that a plugin is (relatively) secure? Yes.That's something WordPress haven't been able to do - so I'd say well done to the EmDash team! And, if I wasn't building my own CMS (with a very similar permission model) then I would probably be trialling it right now :)