The travel outfit is always the most important decision when packing a tiny suitcase. In the worst travel outcomes, you can be stuck wearing this outfit for a REALLY long time. Even if everything goes perfectly, this is the outfit in which you arrive - your first impression at the branch office, or the hotel, or with the relatives.
As much as I adore textured and patterned cardigans, for the Four Pack, I'd stick with a solid-colored cardigan. This amazingly beautiful sweater might get a lot of action, if the weather proves to be cool, and a solid makes it easier to coordinate other items.
Knowing that I've got black pumps, and a tan cardigan, I started looking for a skirt that would fit into the theme, and then I picked up two solid-colored tops that echo the tan and the black. This necklace includes both of my core colors as well as a hint of the grey from my travel pants. A solid scarf in yet ANOTHER shade of tan makes it clear that I do indeed intend to mix a number of shades of one color.
Now you have a variety of choices! This doesn't exhaust the possibilities - you could certainly put either of the solid tops over the dress...