Read these Mercedes documents regarding fitment of oversize wheels and see if ANY are approved for 4Matic.
http://www.w124performance.com/docs/mb/W124/wheel_install_16x7.0_ET46.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_16x7.5_ET31.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_16x7.5_ET37.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_16x7.5_ET40.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_17x7.5_ET42.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_17x8.0_ET28.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_17x8.0_ET30.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_17x8.5_ET30.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_16x7.0_ET46.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_16x7.5_ET31.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_16x7.5_ET37.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_16x7.5_ET40.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_17x7.5_ET42.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_17x8.0_ET28.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_17x8.0_ET30.pdf
http://www.w124performance.com/docs/mb/W124/wheel_install_17x8.5_ET30.pdf