I was checking out these guys on Aurora:
http://www.racknroad.com/seattle.html
I think the Yakima option is exactly what I'm looking for. The existing rack has rails where the raised-crossbar/spoiler-thingys can slide back and forth. There's a knob underneath this that cranks them down in place, and I was thinking there must be a way to take those off and put in a tower for one of the major brands of racks (Thule, Yakima, etc). This way I can put on a ski rack, bike rack, cargo box, etc and still remove them all when I'm not using them. :tup: