Rewritten what? The container runtime will need the same access regardless of what it's written in, and rewriting all of Linux (the kernel) would be... ambitious, although it is adopting rust incrementally.
Some of the issue though is that a monolithic kernel provides more access than necessary to many things. When they made the locks granular, those might be reasonable boundaries for permissions? At this point I'd rather figure out how to make windows drivers work in redox or something crazy like that.
