If you eventually contribute this back, please take into account that, in term of accessibility, pop-ups are not recommended and xinha can't be used but this one can be turned off.
I don't like popups, really! but in order to allow a better user experience, I think here it makes sense. Of course, it could be done also on a normal page first, and then allow pop up (not necessarily a new window but a div) for web2.0 people...
I'm not sure I could do all the stuff, but I can make some screenshots of exactly what I'm thinking of and claim for help :) Maybe I could work together with Rocael.