The problem is that if you want to go prototype racing as a manufacturer in North America, there is no LMP1 option. The 'top' proto class is P2. Added to that is the 'road car derived' engine requirement of the P2 class that Mazda are making a fuss about.
I also hope this is a "US only" effort, because manfacturers teams or other large manufactorer engagement other than selling chassis and engines within the cost cap price range in P2 is IMHO not what fans and competitors are looking for. This class should be reserved for the privateer prototype racing.
