Today's "Meister" review pointed out that the Alternators version of the robot formerly known as Jazz now turns into a Mazda instead of a Porsche. But that wasn't the original plan, because Hasbro and Takara's designers were working on a Porsche mode until they couldn't get the license:
Takara designer Kobayashi Hironori revealed in an interview last December that the first prototype figure made for the line as long ago as 2002 was "a well-known German sports car," but that the company refused the license. Given the timing, it was likely a Porsche 986 Boxster.
(Rumor is they, like Volkswagen, don't want to be associated with "war toys," but it could also be that they didn't want broken panel lines and so refused on those grounds.)