1. I expect wiping any given component to be entirely up to the manufacturer's discretion. If doing so is not trivial and is legitimately required for the repair to proceed then I'd expect the user to be charged for the additional service.
2. Violating manufacturer specifications and being at fault for damages are sometimes distinct. A manufacturer arbitrarily saying "you must not do X" should not necessarily mean that doing X will void the warranty. It might though. Discretion is obviously required.
3. If your car stops working after you mess with the firmware and you take it in to the dealer I imagine they'd charge you to reflash things since the issue was caused by your own actions. That doesn't mean they should be able to decline to cover entirely unrelated defects.
Also I don't think vehicle firmware would be caught up by the original proposal in the first place since cars aren't generally intended to run third party software. There's a grey area with infotainment systems that have an app store depending on if those are viewed as standalone or part of the larger vehicle. However reframing the proposal to revolve around intent would likely leave the firmware on unrelated embedded components in the clear to be locked down so long as those components don't interfere with the ability to freely use the general purpose computing element.
Personally I'd like vehicle firmware to be covered by similar protections but I recognize that falls outside the scope of a proposal about products intended for use as general purpose computing devices.
