The M2 CS is a solid display of how an unrestrained and unrestricted M2 would or should look like. Just looking at the base M2 and at the new M240i xDrive shows you how they were nerfed in favor of the F82 M4 models with the same names. The normal M2 F87 has almost identical laptimes to the new M240i despite heavier weight on the G42 side:
This M2 CS on the other hand almost has similar acceleration to the old M4 CS. It's obviously a bit slower than its big brother but also cheaper.