Wow. I am new to Panteras and by far no expert on brake systems so that renders me unqualified to comment.
What I do know and have seen from my years in aviation is that often a manufacturer will sacrifice performance to bring their product into line with the ability of average or below pilots / drivers. Most are not professional drivers or driving on a track at excessive speeds. I am sure the Tamaso engineers applied a lot of thought and experience when designing the brakes system. I would bet that the valve was used to make the system safer for the average driver in average conditions and was a cost consideration so those alone would leave plenty of room for performance improvements. But how many of us are going to throw their metal mistress around to the point of experancing true heat induced brake fade ? Not me. Those days are in my past and the car is too valuable.
Also what is good on a race track is not always good for a street machine. Putting a NASCAR engine in your Pantera would make a miserable street machine of which you would probably never realize the performance aspect. You want to pay how much for what ? I remember one of my customers complaining that his Fararri needed a $13,000.00 brake job. He said that the car seldom sees fourth gear in LA but you gotta have brakes.
It is a owners prerogative what they do to their car but a guy like me without unlimited funds has to consider upgrades in a cost to real world benefit ratio. I don't need ceramic or carbon fiber brakes. I would much rather have a anti skid system for the cost. Of the brake system upgrades available the ones I would never consider are those that eliminate the emergency hand brake. NFW that's race track stuff not for a street machine. Be smart and think safety because of all things Pantera as with all cars brakes are number one. If you have ever driven ice you'll know that helpless feeling of no brakes.