FWIW, I have never removed my spacers for service, but then again I never went in for suspension service, since I have coilovers. I wouldn't worry about spacers if you are going in for engine work. If Something is funky in the transmission or driveline, it might be worth removing them, but not for routine service.
Also, I have had multiple brake changes with spacers. Here's how to think about removing stuff for warranty...
The Dealer WANTS to do the service, because BMW pays them. The Local BMW Field Rep will rarely if ever question a standard maintenance brake service. Now if you go in for a blown turbo, the field rep almost always looks the car over, this is when all Downpipes, piggybacks, software must be removed.
Remember the Dealer is generally on your side UNTIL the Field Reps are involved, and a brake job will not raise the red flag with BMW corporate, unless you have had like 3-4 in the last year.
2007 E92 6MT SGM: MusicarNW Level 2, Procede Rev 2.5, FFTEC/Vishnu LPFP with Flexfuel Sensor and Flash, M3 Offset V701's, WaveTrac LSD, Michelin PSS, Downpipes, M3 Control Arms, TCKline D/A Suspension, LCI Tail lights, Lux AE's, ER Charge Pipe, DCI's, Mtech Front and Rear, M3 Sideskirts, HPF Stage 1 Clutch