Would the world be a better place if Linux, the BSD kernel behind OS X, and the Windows kernel were all rewritten in Rust? (I don't think it would be dramatically better overnight.)
Seriously, people, you can find kernel bugs at will with kernel fuzzers like syzkaller from Google. Look at https://github.com/google/syzkaller/blob/master/docs/found_b... and weep.
You could claim that eventually the payoff would pay back the lost 10 years. But "eventually" can be a very long time...
So basically, ChromeOS rewritten in Rust? Why not a Servo based UI?