The main change would be to the power supply, as the esp8266 has a far higher (~300mA) peak current than the ATTiny814 used (~3mA).
Currently, an LDO provides 3.3V from the 24-35V motor supply.
This would need to be changed to a buck DC/DC regulator, as a larger LDO at this voltage would need too big a heatsink for the case.