Hi Jason! I think it is great that you're interested in this. The wireframes and other UX (user experience) issues would all be up to you! Also your choice of toolkit, whether it works on mobiles or not, internationalization support, UX plugins, etc etc. Personally, I hope that it will work well on HTML5 mobile browsers--iPhone and Android in particular. I also strongly suggest that you use a TDD (Test Driven Development) methodology. There are now some good Javascript test systems.
Unfortunately I have minimal time to assist with Q2A, my authentication plugin is about the extent of it.
While I agree that the interface could be sexier with Ajaxy-goodness, it isn't an itch that I have time or priority to scratch at this point.
Remember that there is no shortage of good-ideas in the open source world. The shortage is of skilled developers, like GidGreen, who are willing to put serious time into the software. I'm glad you're willing to join the ranks of serious open source developers.