I was wondering if there is a way to create a nextgen gallery with a function, so that I can hook that into my front end post creation setup. The gallery could be completely empty or be created with the featured image of the created post.
I think you're just trying to get a featured post slider. If this is the case, you could go with a much more robust and expandable option like Nivo slider. You'd have to code it into your theme yourself to get your desired result (shows recent posts automatically), but it's definitely possible.