6 - there's a way to close registration up, so I think building an invite box in the admin panel might not be too difficult
7 - right now there's a moderator threshold you can set in the control panel (ex. if you hit 1000 reputation, you become able to delete posts). At some point we'll implement a thumbs down as well
8 - right now we have the youtube, dailymotion, and vimeo plugins. For images, you'd need to use markdown syntax ex.
![alt text](limage url)although a plugin for this could be possible as well
I think everything else will find themselves implemented via plugins at some point in time. All of them are valid and pretty important things to have!