Complete waste of time and $ at this point, if you ask me. Get a vehicle w/the inlets matching infrastructure in your area.
There isn't physical room on a gen 1 Leaf w/CHAdeMO under the charging door for the 2 extra pins. I guess you could do it on a Leaf w/no CHAdeMO and have the J1772 inlet w/SAE Combo sideways for room. Or, you could add the SAE Combo inlet somewhere else like under the hood ala JdeMO (https://shop.quickchargepower.com/JdeMO ... MORav4.htm
I think you misunderstand where the charger is. For DC charging, the charger is outside the car. The car's on-board charger is bypassed.
CHAdeMO uses CAN protocol. CCS uses GreenPHY, so someone needs to emulate/spoof a car talking that. And, you'd need more high voltage lines running to the same place where the CHAdeMO inlet ultimately connects to.