I am not an aircrew mate and I have no knowledge of the MR2's fuel system but it strikes me that the chaps who are flying the MR2 need a reasonable degree of assurance that the ac is safe. Clearly this does need to be balanced against the need for the operational task, which I understand is important, but whilst some risk may have to be taken it would obviously be wrong to expect crews to fly in a death trap. I am quite sure that the MR2 is reasonably safe because the MOD says that it is and it would not be in the MOD's interest to be mistaken because of the damage that would be done if it was subsequently found to be wrong.
However, I think that if I was the leader who had decided that the ac was safe to fly, I would be able to think of no better way to persuade my chaps that I had thought the matter through than to fly a couple of missions with them. This is easy for me to say of course because I am neither an aircrew mate nor an AOC nor CAS (and will never be) but nonetheless I have always found that of all leadership styles, by example is the most effective.