Here's my thoughts for what its worth
I guess it all comes down to personal preference. Also most schools have some form of corporate wear/uniform. Having met a guy in Canada some years ago who survived a post crash fire I have given it much thought. I like wearing gloves, some dont, leather boots or shoes seems fairly standard, I certainly recommend them rather than trainers.
The shirts I am provided with are not 100% cotton ? Though I do go for 100% cotton trousers, and tee shirt/underwear. Its got to help surely ! may well invest in a flameproof type jacket and or trousers, (be nice to find somewhere fairly local so you can actually see/try on the stuff, also what is the nomex gear like after a few too many washes, can you get the fire poofing re applied???) to wear a flight suit at work would not be part of the uniform??
Would be happy to wear a helmet I personally have no issues at all with them, the looking like a pill@ck argument doesnt wash, particularly if more people start using them. Though you would constantly get the "where's mine?" question from the guy or girl next to you, not sure what the boss would say when I am doing trial lessons in it though, may put the fear of god in some of the more nervous passengers.
I guess it all comes down to how the student percieves "the danger" Some people wil happily fly in shorts and flip flops
!!!