The standard male mechwarrior attire while in the cockpit is a pair of shorts, and maybe a tank top with a cooling vest, lightweight botos and maybe gloves. I'd assume the women wear something similar. You could wear whatever you want, but it gets pretty hot inside the mech, with the fusion engine, weapons, and even getting hit witrh soem wepaons, generating alot of heat. I don't have numbers off the top of my head but i'd guestimate that temps from an average battle can easily break 100 degrees.Even in a cool runnign mech, that can dissipate all of it's weapon heat your still looking at a good 75-80 degrees.