selectively disabling atime updates?

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

Walking a directory tree (e.g. during a backup) unnecessarily updates atimes.
Mounting -o noatime is not an option because the atime updates are needed
elsewhere.
Is there an option (overlay mount or such) to present a file system noatime
(or even read-only) to one process (or at one mount point) but "normally"
to other processes (or at another mount point)?
It would probably suffice if the NFS export would update atimes but local
access wouldn't.