the fv-1 has stereo inputs and outputs on the chip. I think using different effects in each audio path would put some limits on what could be done with each side since the chip has limited audio processing resources. Space for extra in/out jacks on a pedal, and needing more pots to adjust the second channel is also an issue, as well as space on the PCB for separate audio chains to be buffered, mixed, output. Also not clear how much utility most guitarists would gain from a stereo output with different effects, since we usually end up plugging into one amp. Seems like it would be possible to do a stereo FV-1 pedal, but those are my guesses why you do not already see them.