You mean the housing goes all the way through the headtube and the cable stop on the downtube won't accept a barrel adjuster?
My first idea is that you can always use an in-line barrel adjuster anywhere you like, usually close to the ergo powers.
You can get away without a barrel adjuster at all, too. The RD has one anyway and the FD needs a little more patience to adjust, but it's not too difficult.
"Nothing compares to the simple pleasures of a bike ride," said John F. Kennedy, a man who had the pleasure of Marilyn Monroe.