Yes, putting all our eggs in the "POSIXy, monolithic kernel implemented in C with MMU-isolated processes, ambient authority, shared mutable state concurrency" OS basket feels unwise.
Well, Haiku isn't too different from that anyways. The kernel is very much C++ and not C, and does have certain hybrid tendencies (it's a lot less monolithic and statically linked than Linux is at least), but most drivers still run in kernel space and the process model is very POSIXy, with most of the other attributes you listed, as well...
