Reflashing the ecu does not create a voidable warranty situation, to the best of my knowledge. There are federal and state acts that are generally much friendlier to the consumer than the supplier (dealer). There is also an extreme amount of case law on this very issue, which favors the consumer (again, in nearly all cases, save for gross negligence). At most BMW could naturally attempt to deny coverage on the ECU and items it controls. Though BMW could also say your bike can't be released to you, because you've not installed seat belts. Hypothetical,absurd,examples are the reason lawyers exist.
To that end,BMW can say anything. It does not mean what they are saying is legally sound. In regard to the ecu example, It's unlikely they'd get far in voiding the warranty. As a side note, something does not become automatically void, in most cases. Rather a contract, of which a warranty falls into the category of, is "voidable." But, again, it is very difficult to do. The M.M. Warranty Act provides a framework, along with more recent case law which puts BMW on the defensive. If someone at your dealer tells you that your warranty is void, and they refuse to work on your bike,ask to speak to the manager,but also call BMW customer care, and while you're at it, it's a good idea to ask to speak to the regional manager.
BMW techs like to pretend they attended law school. They did not, at least 99.99% of them; that is not to say thatworking on high end sport bikes all day is not a fun and equally important profession.But, they (most BMW dealer personnel are in no position to quote warranty laws to you aka- scare the crap out of you, believing you're brand new bike's future repairs are now your responsibility. That's just not how the world works,luckily).
Personally I'd be comfortable reflashing my own ecu, if I knew how. Again give bmw customer care a try. They can be very helpful (if you catch them on a good day). Otherwise a lemon lawyer, who is paid by the manufacturer,not out of your pocket, can usually help you within a matter of a few days.
Worst case is BMW could succeed IN VOIDING your warranty;though they could not void the entire warranty for playing with the ecu. For example- while it's unlikely bmw would succeed in voiding any part of your warranty, if by some rare chance they did find a way to void your ecu warranty, your suspension warranty would still be in effect along with every other part of your bike, that is covered by the bfactorybwarranty.
Send from my iPad. Please excuse any errors.