Here's an interesting idea. As opposed to United looking for a new regional feeder to its Dulles hub, why doesn't United and US Airways broaden their code-sharing agreement and feed United (particularly with west coast bound traffic) from US Airways Express markets?
http://biz.yahoo.com/djus/031223/1017000686_2.html
http://biz.yahoo.com/djus/031223/1017000686_2.html