I've been down this avenue...Realistically the only good thing about it is the engine.
I decided against it for the following reasons:
1/ I'm 24 and the imagine is all wrong
2/ it's not a good lookin at the Z4M
3/It's 30k+
4/It's 30k+ for a high mileage one
5/It's 35k for a decent one with lower milage.
6/Even the above is older and warranty then becomes an issue
7/My Z4M hasn't been the most reliable...Not as a BMW should be, all sorted now right enough, but the M6 is 10x more complex
8/I only really do town driving and i get 17mpg in the BM, thats 170miles to a tank, a tank a wk. £3k+ on fuel a yr. you can easily add another grand to that for the M6
Just my thoughts, as above the engine is a masterpiece, but that alone isn't enough for me to sell mine and have to subsiquently find 14k to replace it with a equal mileage Older BMW....
No.