The Diabolique RS200 was done by BBA two years ago. I'm fortunate to have one, partly made, just need to complete the chassis and interior. I got it free from the guy who paid £300 for the Celica kit..
I have never understood why the GrpB cars have been ignored by the mainstream manufacturers. Aside from the Tamiya Pug and the Hase 037, it's been pretty lame. Can you imagine an S1 from Tamiya(!) or a S4 from Hasegawa. Surely these kits would be popular.
I admire Scuderialab guys for doing the 5 Maxi. They have an S1 in the works too.