Just a thought that maybe the Sierra DTM can replace the M235i **IF** we want to keep the cars "period correct".
In my own testing with the AI driving, the 190E Evo II does 54.4 around Barbagallo, the M3 E30 DTM does 54.5 and the Ford Sierra DTM (link at the bottom of this post) does 54.7.
The M235i does it in 57.4 which is a few seconds slower (although, again, this is with the AI driving), so this could be used as the "punishment" car for the faster drivers (pending further testing of course, just in case it was a fluke that the AI was so slow in my testing).
However, again, in the sake of possibly keeping it a bit more period correct, there is also the Vauxhall Cavalier BTCC '90 (which in my testing did a 55.3). In addition, there is also the Honda Civic SiR-II Group A '91 (Barbagallo in 56.0). I'm pretty sure all three of these mods were made by Malagoli, who does some fine work in my opinion.
Ford Sierra '82 (including DTM and Group A versions): http://www.racedepartment.com/downloads/1987-ford-sierra-cosworth-rs500.4840/
Vauxhall Cavalier BTCC '90: http://www.racedepartment.com/downloads/1990-vauxhall-cavalier-btcc.8566/
Honda Civic SiR-II Group A '91: http://www.mediafire.com/download/12t3pto1ahpys0j/CivicEG_GRA_1.0_NoSkin.rar
Of course these would all require more testing to make sure everybody is happy with them and to make sure my AI testing was accurate.