I don't see the relief pitching, DH, or backup C positions as being places you'd address by moving a starter. Obviously it would be nice to add some shiny parts, but it's not necessary. IMO the biggest areas that absolutely need to be addressed with proven talent are 1B and a corner OF spot. And there are so many options available that it's hard to imagine not getting two of them.
Trading a starter just opens up a very big hole, and the only free agent arms are Nova, and Hellickson, who I'm sure nobody wants to sign.