I use my Turbo Chameleon a lot. I use additional cores a lot also, so much so that I have different SD cards for each major core. With the SD2IEC you can create a swaplist to switch between D64s. Could something like that be implemented? Put a text file in the root folder with a simple instruction to auto launch a specific core? If that text file is not found, it would load normally. The SD card with MimigAGA install could auto launch the MinimigAGA core. The SD card with Atari ST install could auto launch the Atari ST core.
Not sure how easy this would be to implement, so kindly asking here to see if it is.
Thanks again for such wonderful hardware.