I feel like even in a modern setting Pantheon would wear his helmet, regardless of what else he was wearing. Day at the office? Suit, tie, and Greek aesthetic helmet. Out for a jog? White undershirt, basketball shoes, and helmet. Tinder profile pic, just the helmet. Out on a date, well polished helmet and whatever else he felt like wearing. Helmet.
//I did my share of Pantheon in modern clothes