Actually, it's not that important in the bigger picture.
Yes, it a breed characteristic and trait, and one point that makes them much loved, but when talking about the Keur and a bald Friesian, it's much ado about nothing. The Keur s based on important matters...conformation, gait and temperment. Yes, the judges will look at the hair, but it's nothing more than cosmetic and won't affect a good quality horse! The Keur is not an "in-hand halter" class.
As for the feathers, a lot of people will shave them off for medical reasons, if the horse as scratches, or they want to prevent
scratches if their Friesian is kept in wet conditions. I've also seen some Dressage competitior's shave the feathers off...maybe to get a more streamlined look (or sometimes I think it's to hide the fact that the horse is a Friesian as many people still tell me Dressage judges are biased to Friesians??
Personally, I hate the look of the feathers shaved off. Mostly because Friesians have dinner-plate hooves, and without the feathers the legs-to-hoof look big and clunky.
And while I adore the enchanting mane, Friesians do look good with a "mohawk" 'cuz it makes them look statuesque, chisled and quite polished. That's how Friesians were presented in the big driving competition in Africa (where Dutch settlers brought them). I'll try and scan a picture...