svn switch --relocate
a user's working copy with a hook script? Looks like you are confusing the terms. Nevertheless I advise you to check the following warning in SVNBook:
While hook scripts can do almost anything, there is one dimension in
which hook script authors should show restraint: do not modify a
commit transaction using hook scripts. While it might be tempting to
use hook scripts to automatically correct errors, shortcomings, or
policy violations present in the files being committed, doing so can
cause problems. Subversion keeps client-side caches of certain bits of
repository data, and if you change a commit transaction in this way,
those caches become indetectably stale. This inconsistency can lead to
surprising and unexpected behavior. Instead of modifying the
transaction, you should simply validate the transaction in the
pre-commit hook and reject the commit if it does not meet the desired
requirements. As a bonus, your users will learn the value of careful,
compliance-minded work habits.