Obviously the tyre and clutch heat models are not finished yet. You have to start from somewhere, and I'd rather take brakes that heat wrongly than brakes that don't have heat modelled at all.
I think its important, as it adds another depth to racing. There are a few australian endurance races where you have to change the brake pads atleast once during the race too, which is always interesting to watch!
I think it is especially key to the road cars, accomodating brake fade is part of many a race where uprated pads and fluid/hoses are all that are allowed. I can't imagine the XF GTI has a set of 12pot AP Racing jobbies on what is essentially a £2k car.
It is also important for the single seaters, as they have brakes designed to opporate at very high temperatures. From my very limited Formula Renault experience, when you go out, the cold brakes are absolutely terrifying to start with, and it is only after a few hard corners you can start to get that "landed on an aircraft carrier arrest wire" braking going on.
Lastly, the code is pretty much all there from the tyre heat model. I know there are some changes such as how much air flows over the brakes for a given speed, and how much heat is transfered accordingly, and how long the pad heat takes to soak into the calipers and at what point does the pad surface start converting to a gas which lubricates the pad on the disc, and when the fluid starts boiling, yadda yadda yadda...
but to start with, all you need is brake cooling as a function of forward motion, and heat being added during braking as a function of brakepressure, and braking effectiveness decreasing exponentially with heat after 270 degrees or similar, tune using test patches to check appropriate drivability.
An Uf1k competitior in the form of the XF body (1,1 I4 with ~55 bgh, a.k.a. Punto gen. 1) toasts it's brakes after 2-3 hard brakes. Like going from 100 kph (and 4th) down to 2nd (30ish or maybe even less) on a downhill braking HARD. The brakes started smoking after that. Literally. And i overheated them driving carefully (watching the brakes mainly) on a long descnet - something like 1000 vertical meters of descent.
Except for the way people drive RB4, and to a lesser extent FXO. High brake force, and still on the throttle whilst braking hard to keep the turbo spinning. In those extreme cases brake temperature could play a real part.
Good quality brakes like the ones that should be on the FZR shouldn't fade during a race, so sure implement it but don't if it's going to get messed up and they fail after 1hour of driving.
I'm sure they'd do it on a similar scale to how the clutch heats. Meaning, some cars will heat up faster than others but for the most part you have to be pretty careless to overheat your brakes.
I would prefer brake temperature/fade be modeled, as it more closely mimics what happens every time I drive in a spirited manner.
It's hard to overheat 11.3" rotors and track-compound pads in a VR6 Jetta, but I find myself glowing rotors and igniting pads after a heavy canyon-carving session. Says one of two things there, either One - I'm driving too closely to the limits of my car's breaks; or Two - my driving style provokes excessive use of the brakes. I'm inclined to think the former before the latter, but both could equally be true.