@m5stack does the USB module go on top of the FACES and under the Core?
Yes, I would use an intermediate driver for the stepper itself and use the MCU + USB module to send signals. I mostly assume MCU pins do not do any work beyond to send/receive signals. ESP project above uses 3.3V relay to switch 12VDC. The chipKIT project referenced above uses Sparkfun Easy Driver product. Another application with a more hefty stepper uses "Rugger Circuits" designed Rugged Motor Driver shield.