Ok, I got an email back from my region’s SCCA Tech.
"You are correct IT cars are not required to have an on-board fire system, only a hand-held fire extinguisher. If you do put in an on-board fire system (which I would recommend), it can be either a system certified to SFI 17.1 specifications or those listed by the FIA on Technical List No. 16. "
The bimmerworld SPA system is a FIA listed system, so this is good to go. I am buying it and some tow straps.