Trimble, the reason that it is hard to get good research going using OMM is because it is hard to quantify the results. Drugs are easy because they have certain physiological pathways that they effect. Test someone for presense of a certain disease before meds and after meds, if the disease is reduced or gone, then it works.
OMM on the other hand treats Somatic Dysfunction, and only Somatic Dysfunction. It is a treatment for the Host component of illness, kind of like therapy with the mental patient. Listening to a patient and giving feedback does not change the way chemical receptor are working in the brain for instance, it helps the person, not the disease. You could make the argument that most psychiatists practice with osteopathic priniciples because they address both the disease state through drugs, and the host component through listening and therapy sessions.
Somatic Dysfunction is a problem with the body, not a disease process. Some people can have a ton of dysfunction and adapt quite nicely to it, others can have a little and become totally open to disease. As far as what OMM could do in your field, it would do what it does in every field; make the patient feel better and raise their potential for wellness by removing Somatic Dysfunction. If the patient feels better, the body should respond better to medical treatment and heal better on its own.