I really like the look of sleeves with your corset skirt, but I'm not sure that lacing on the dress under it won't look odd. By the same token, I think if you get a dress of close to the same color, if it doesn't match, might not work quite right.

Gorgeous corset skirt, by the way. (And while I think you should absolutely buy a new dress, I also really like what you're wearing under it already. You could wear the Bella by itself, and the corset skirt with current stuff, at different times at the conference, maybe.)