Funny I came across this thread as I was doing some renderings about the future M2 GTS/CSL...
Here's my M2 CSL... Well, at least what I think it will look like,
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Subtle visible differences compared to the stock M2: You can see the differences on the animated gif
1-Wider front and rear tracks with wider front/rear wheel-arches, Bigger air intakes (air curtains).
2-carbon fibre roof.
3-Wider wheels all around on fully adjustable coilover suspension.
4-M4 GTS/ M2 MotoGP rear wing
5-M2 MotoGP carbon fibre front spoiler + M performance front and rear winglets.
6-CCB brakes from the M2 MotoGP.
7-Bolder colour palette with reference to BMW's past Motorsport icons
Non visible parts are:
1-CFRP hood and bootlid
2-Water-injected N55 engine + e-drive (?)
3-Part CFRP chassis (à la 7 series)?
4-Possible rear sear delete + roll cage
I'll work on a version with M mirrors in carbon fibre later on...