The hardware of the VESC and regular hobby ESC is not that different. The main and only significant difference is Current sending + CAN. Other differences you mentioned are not that relevant to express difficulty.
The difficult bits of ESCs are FET driving + routing, voltage sensing and if desired current sensing.
There are 2 mayor opensource firmwares that are implemented by “chinese” manufacturers. There are even a few opensource HW BLDC ESCs.
I don’t want to sound to pessimistic but if you say ESCs are not that difficult you are very skilled ( by the many ESCs you already designed + made + used ) or there is a big smoking surprise waiting xD.