I arrive at the airport using a different building from the pax. I use a different checkpoint to get through security, even if I had a hat I would not wear it while doing the walkround- so the only time when the pax are likely to see me, it is irrelevant. By the time the pax board, I am in my seat, probably doing paperwork. A boilersuit be overkill for the walkround, so in terms of presenting a professional and reassuring image to the pax, the best I can do is have an ironed shirt and comber hair- that is all they are going to see as they board, even if they happen to look up as they cross the tarmac.