Depending on skill, Claude already does this when creating new skills with their skill-creator skill (what a sentence), it's pretty neat. It creates ~6 subagents with and without the skill and judges if they differ in performance.
As I understand it the majority of back pain cases have unknown/undiagnosable causes (and the only "treatment" is either more or less exercise and painkillers),so unless there is an actual physical deformity a psychiatrist is as qualified as anyone to diagnose it.