At the end of the day, your M3 is still a convertible. Racing heritage? Who are you to mock BMWs marketing and sales team when you fell for it and bought a convertible M3?
SMG is automatic, whether you like to think it is or not.
“BMW offered a system simply called “sequential manual gearbox” (SMG) on the E36 M3, and later “SMG-II” on the E46 M3. The BMW SMG transmission has both automatic and manual shift modes. Inside the different modes there are different programmes, with six settings to control the upshift/downshift speed for manual operation, and five settings for automatic mode.”