Except that sports car racing is and always will be CAR oriented. It's one of the hurdles that GARRA is trying to conquer by giving drivers more recognition than individual car types.
(notice, the big news out of Daytona wasn't that a Riley Pontiac won, but that Max Angelleli and Wayne Taylor won)
JGTC already has a multi-national grid of drivers (Krumm, anyone?) so bringing in an even bigger mix of drivers won't help a damn thing.
Cars attract people to sports car racing. Bring in more cars, bring in more fans. And the way to bring in more cars in sports car racing is to have a strict but open ruleset that encourages close competition. The minute one car type is favored or one manufacturer begins to completely outpace the rest of the field, say bye-bye to the rest of the field. They'll spend their money elsewhere, and so will the fans.
Ever wonder where the Speed World Challenge fans came from? They're two groups of people, primarily. Folks who enjoy SCCA club racing and like seeing it on the Pro level and folks who used to watch Trans-Am. SWC grabbed the Trans-Am fans because Trans-Am folks were sick to death of seeing Paul Gentilozzi and Rocketsports dominate with their Jags.
SWC has Audi RS6's, Viper Competition Coupes, Cadillac CTS-V's, Volvo S60R's, Porsche 911GT3 Cup Cars, Corvette Z06's, BMW M3's, Saleen Mustangs... The list goes on and all of them have a realistic shot at winning.
You bring out racing like that with the level of modification JGTC has, and I can predict big crowds, but it has to be fair, balanced, and strictly policed. The SCCA tech guys who run SWC are tech nazis. Each individual make of car has a very strict "modification index" that says exactly what can and cannot be done to make the car faster and in fact outlines some of what's done to slow down the cars to keep the field together.
There's the recipe for the perfect "Super GT". Speed World Challenge, except with more modification and pricier cars.