IMO, if true flex-fuel programming and interface hardware were already available in the current ST ECU, then I know of at least 2 tuner software/hardware vendors who would have it available in their software, HPTuners and Cobb Tuning. AFAIK, ZFG uses HPT exclusively. Several other top tuners use HPT and/or Cobb.
If Flex-Fuel capability was at the top of the “functions wanted” list for advanced tuners like ZFG, and it was “easy to do”, then HPT and Cobb would likely add code to perform it. If it was already there for use, then
FYI, there’s already more than a few “custom/customized” bits of code included with the current HPT and Cobb software.