I agree.
Writing in Rust might make the iteration/development process itself a little easier, I'll give it that.
I also like the idea about creating a system that does its best to isolate components and create a trustworthy environment. I'd probably pull the enforcement into the kernel though - not quite SELinux/grsecurity/AppArmor, more a system that completely isolates everything.
Kind of like the direction Linux is going with containerization, but developed that way from the start.