Late to the party, but that's awesome work!
I am looking at creating my own decoder and documenting all codes on the BMW CAN bus (at least for my G87), happened on this thread.
Quick question for the OP: have you checked to see if CAN H and CAN L are broken out on the OBD II port? According to the spec, they should be available on pins 6 and 14, respectively.
Also, besides engine / performance data, have you also seen messages for the rest of the onboard systems (infotainment, door lock, lights, etc)? I would imagine you have chosen to ignore those for your project.
In my E46 days, I'd tapped into the CD changer twisted pair for all "ibus" messages and used steering wheel buttons to operate Paul Stroffegen's MP3 player (
https://www.pjrc.com/mp3/index.html).
Here, I'm interested in unlocking some hidden options that are in BMW's firmware.
OP, if you're still working at the list of codes, I'd be happy to contribute.