I think this is a bad idea, what if you need to make an emergency stop?? For example, a guy with a faster car ends up getting squirrely and in your lane, so you hit him because you can't get slowed down?? Or someone steps in front of the car after you come out of the water box, near the start line??
Just fix whatever is wrong with it, brakes aren't black magic. If you have the money for a track entry fee, you have the money to fix the brakes. don't risk injury to yourself, or worse someone else, because you are too lazy to fix it.
If the track tech knew you had the rear brakes disabled, they wouldn't even let you in.