It would only be possible if a limit were enforced on all non-primary namespaces.
However something that has been /possible/ for a while (but not in practice done) would be to elevate root process priority over other processes. Probably not done due to daemons needing to run as root (which is decreasing as they're able to drop privileges these days).
Root has had the ability to assign negative nice values since long, long ago. Non-root users can only assign positive niceness. The range is -20 - +19.
In theory this can give higher priority to a process, but if you cannot get into the run-queue at all (fork bomb), or the problem is in kernel space (e.g., I/O access, hang, or a kernel space loop), then it's not going to help you much.
And, sadly, most of the really hard hangs are kernel space. The general fix is to cut off all network requests/incoming jobs, powercycle, dig through logs, and try to shunt a future hang. (Sometimes just cutting incoming jobs will stop the hang, too)
However something that has been /possible/ for a while (but not in practice done) would be to elevate root process priority over other processes. Probably not done due to daemons needing to run as root (which is decreasing as they're able to drop privileges these days).