"Also I would really like to meet one of these "customers" who are so terribly fragile that they'd throw a contract in the bin over employees of a prospective service provider being dressed one way or another. They would be very fun to troll but I have a feeling that they do not in fact exist."
My neighbour worked as a window cleaner for many years, and ran the company for a few years when the boss decided to semi-retire. During the handover, his boss told him to always have a shirt and tie in the car for when he was delivering invoices and dealing with customers. They might be window cleaners but they could be professional about it dammit!
A couple of weeks later he was asked why he was wearing a shirt?
The customer suggested that his working t-shirt and trousers were fine and he'd never understood why $boss had always gone and got a shirt out the car - he was a window cleaner and they were his working gear. Just because the customers (solicitors) were wearing suits, didn't mean he needed to put on a shirt in order to talk to them - the company's professionalism would be judged on how clean the windows were!