I did some work on a toolchain used in automotive (and other industries) to proof^W prove certain software properties related to safety. This is already a massive effort, expensive to build & maintain - but after all a small cog in the whole machine. (Using Rust over subset-of-C would deprecate maybe half of that work; at most I'd guess). The hypothetical team would take a decade or two to replicate just that cog.

Yes, having the whole machinery available as FOSS would be awesome and I'd like to live & work in a world in which this is the norm (Hello, Star Trek?). But all this requires very talented people, many of whom studied and racked up student debt, want something to eat and a place to stay. We first need another paradigm shift to make this kind niche open work sustainable.

Oh, and if you ever find yourself in a car with critical components not checked with that kind of toolchain: I strongly recommended getting out of there asap ;-) For all the excellent people building that software, there will always be some who'd be better writing mobile apps instead (or anything else that cannot kill people).

(btw: You asked me about the setpoints of the 12k 3P Deye inverters a while ago: Seems to work nice for me with my basic "just the inverter + PV + battery" setup. Though some people report trouble when using AC coupling with another inverter; in that case the Deye seems to swing more around the setpoint).