I don't care for the fictional LMP's put into the game. Also the Mclaren F1 longtail and the Mercedes CLK-LM aren't LMP's, but GT's.
And you cannot join a field of Audi R18's in your BMW V12 if you want to be competitive. For us Le Mans fans, there just isn't any content available if we're to be honest. That's why I always loved Gran Turismo for offering so many Le Mans cars.
I will say, though, that the GT3 field is brilliant in this game. I'd only like to see the 458 GT3, the C5R or C6R, and a 911 GT3 RSR at some point in the game. Then I would be really happy just playing this game for GT3 championships only.