I think it's the other way around. No one looking at a mustang is interested in an M3, but with the newfound performance in American muscle cars and the leaps and strides made in the interior department ... m3 customers are probably starting to look at muscle cars.
There's been comparisons with the M4 and the Camaro SS, as well as the GT350 and both cars kicked the crap out of the M4, have a (somewhat?) comparable interior and cost half as much. Unless you're a 100% snob, its hard not to cross shop in that direction.
From my professional experience with Ford - probably 80-90% of my customers like muscle style, and hate the Euro stuff.
The Euro customers can come to the Muscle car side, but Ford should not cater to these people. They're 'extra' - Ford is the #1 selling brand for a reason, lets not muck that up. Imo...
The GT350 was a TOTAL flop.