I think the frustration muxi feels is that there are gt cars already in rf2 at the moment and what's missing is a prototype. Now ISI are looking to add the historic cars in which is great news, but a modern lmp1 would mean that rf2 has basically all the main types of cars in, from open wheelers, historical, gt, touring and the odd 3rd party road car mod.
I'm sure this will be of really high quality when it's out, but personally i think maybe one of each would keep everyone happy early on so we can see how the two types feel and look, not just one type (gt)