I was wondering if you would be interesting in adding support for BuddyPress.
Here me out on this one because you've solved some problems already with your plugin and it might be fascinating to see some collaboration here. Sbrajesh, who runs BuddyDev, also has a Front end posting plugin, but your's is far more mature than his. More importantly, he has created a plugin for BuddyPress called BuddyBlog, which enables user to manage and edit their posts from within their BuddyPress profile. It also has the nice feature of being able to visit a BP profile and seeing a user's posts.
Brajesh's BuddyBlog plugin uses his front-end posting plugin as a dependency, but as I mentioned yours is more robust. One of the things that you've solved already is how featured images are handled (and all the other things that you've figured out). If somehow, you and Brajesh could collaborate, so that the dependency for BuddyBlog could be User Submitted Posts it would feel like a match made in heaven for those of us who build sites around BuddyPress. The maturity and level of development with your plugin, along with Brajesh's deep understanding of BuddyPress on the complimentary plugin would make for a very powerful integration.
(of course, I have an ulterior motive since I have client that currently uses User Submitted Posts, but would benefit from the added interface of BuddyPress/BuddyBlog post management)
Hoping to inspire - I'd love to hear your thoughts on this!