I did bring in outsiders to consult on my therapeutic relationship three or four times. I found it very helpful to have that objectivity and have some space to gain clarity, so I absolutely see what you mean. I'm not sure a therapist would be willing to see a mediator in general, but actually, I do recall one case of it mentioned here on PC, so maybe that stratagem could make a difference if a future serious rupture occurs with your current therapist. Plus, it sounds like you've gained lots of insight overall anyway that must help some in your current therapy.