So the folks at the University of Cambridge are proposing a full replacement to mmap primarily to gain W^X support (secondarily for CHERI work). Brooks' face when I mentioned HardenedBSD has a more strict W^X implementation (PaX NOEXEC) than #OpenBSD was fun. He also seemed a bit surprised that #HardenedBSD is more than just ASLR.
CHERI's doing some great work, but it'll take multiple decades not only for CPU vendors to integrate the work, but also for general consumption.