Sure, Ada/SPARK is another option. Listing out the various potential choices people can make is not especially interesting to me. I don't personally care about Rust. I care about people taking action to solve a frankly embarrassing problem in our industry.
That would, depending on implementation, either have limited impact (if it only applied in the context of a commercial relationship), or destroy FOSS (if it didn't).
The usual argument, health inspections don't destroy the little business selling sandwiches on the corner, or street regulations and those doing their own home made car.
Also I should note that NVidia, prefered to go with Ada/SPARK instead of Rust for their automotive firmware.