I actually have a mods planning spreadsheet and my next parts are indeed the front upper and lower arms, the rear subframe bushings, and the M3 e93F/e92R sways.
Then the second phase is GC coils with M3 rear lower camber arms. I have yet to hear if there are bushing differences between non-M and M rear guide rod/upperlink/track strut arms. If you definitively know, I'd like to hear it!
The second phase is a ways out, budget wise. I have spent a lot on her this year already!
Oh, and as for BBK, I'm first going to custom-build my brake duct kit and then see if she needs a true BBK. In fact, in between those two, I will probably try dedicated (vs hybrid) track pads and maybe RB rotors before dropping serious coin.