I did another symptom hunt on Google and found a thread on the M5Board with very similar issues. The same things were experienced by a few people, turned out to be either the radiator fan, the alternator / voltage reg, or the DME as the main culprits.
There is no doubt that all BMW can bus setups and modules throw fantastic red herrings, how many times has my SMG apparently been on the verge of dying and red cogged - when the reality is the battery voltage is just lower than ideal on cold start. Currently this is all covered under warranty, so I can't really reach out to Promo without complicating things just yet. Thanks for the details though.