A combined set of regulations for all GT style racing would have a huge and dramatic effect on racer numbers and manufacturers would find it much easier to jump on board. If a Manufacturer has half a dozen potential rac series and could conceivably sell 20-30 cars there's potential to even make a small profit on GT style racers for the lower classes. Although Porsche, Audi and others already make GT racers McLaren, GM, Mercedes Benz, even Lamborghini and possibly Ferrari could be enticed into something like this.
Lamborghini, Ferrari, McLaren, Mercedes AMG, Corvette and BMW along with Audi and Porsche all make BoP compliant GT3 cars competing very competitively in a wide variety of series including Blancpain Endurance (50+ grids) and ADAC GT Masters (40+ grids).
If it means that we can have the variety and volume of cars currently competing in GT3 (and GT1) championships racing at Le Mans, then I'm all for it!
GT1 is effectively dead, the grids last year were only around 9-11 cars and this year many of the entrants were glorified GT3 cars. Infact the Hexis McLaren MP4 GT3 won several GT1 rounds and also won the final Blancpain race.