VW wouldn't design and sell a car that couldn't stop from its maximum speed and as we're not legally allowed to do even half of it in the UK the GTI's brakes are more than up to the job.
As for the point of remaps, there are other aspects to performance beside top speed, acceleration and overtaking ability are merely 2.
I still maintain that a 300bhp Golf only driven on the road doesn't require better brakes than a 200bhp one. It isn't any heavier and it shouldn't be going any faster. Same weight, same speed, same brakes!