Hi mux, yes now We're aware about the 12V battery power drain and we're thinking how to stop the OBD2 platform to query the CANbus while it's not necessary, shutting it down.
Btw, I'm well aware about this thread and I read it all, but you shall also know that 2018+ Leaf info are missing since the gateway added with 2018 model.
You're suggesting to connect to the regular CAN bus instead of the OBD2 port, but I haven't found any wiring information about how 2018+ are working now. OLD models shared different buses on other OBD pins (EVCan, QCcan, CARcan etc) but this apparently isn't true anymore.
So querying the gateway with 7XX IDs seems the only way to get Leaf's variables.