That's exactly what anybode else would do. The idea is to take any business rules or any redandancy and bring it over a middle tier. But you still need an interface to communicate with a middle tier. There is no need to biuld that interface into a middle tier. For example I'd like to by your finacial business solutions (middle tier). But I'd like to have my own interface (different language users speak). But your server comes with an interface???? Another story to distribute interface solutions.
Mark