Hi Timekeeper, I know it is extremely frustrating, I myself got to the stage where I felt like saying "stuff it, I'll order the part myself and do the repair" even though I wouldn't have a clue how, I felt it would be done in a few days tops, part ordered and received straight to me within days. Screw the warranty right, whats the point of having a bike you paid for (paying for) that can't be used. Also hard when you have no other bike to ride. Thought I was just share some of my frustrations so you know you are not alone. I'd do what you suggested, get in touch with a BMW rep and see what they can do, this customer service is very very bad (the repair shop in the end represents BMW) and will push people to other brands.
My bike's rear light (G310R) went out entirely months before my Stator died, I pulled over at that time, re-seated the connections under the seat and that fixed it, or so I thought until the Stator died, which happened exactly how you described it, flat battery while riding, just after riding, lights still on but very dim, electricity sound going through the bike when ignition pushed but bike stays dead. I wouldn't ride your bike at all, too dangerous, until the shop you take it to repairs it.