stalling commits until approval

Does anyone know of a, relatively, simple way to block commits,
without approval? For the sake of context, here's the actual need:

The company I work for has decided (correctly) that we need to keep
out system configuration scripts (puppet) in Subversion. Migrating
all of this is a rather trivial task but adding sanity to changes is
one of my top priorities. Since puppet has the power to do "Bad
Things," when you mess up a config, we'd like to require change
approval. The suggestion I've heard, thus far, is to have release and
development branches and integrate from the dev branch, once a change
has been approved. While doable, this isn't the most scalable
solution. What I'd like to see is something more like this:

1) Admin makes a change and attempts to commits
2) Pre commit sends out a request for peer review
3) Second admin either approves the change or adds feedback
4) Once approved, the original admin can now commit to release branch

Using dev and release branches, something like this seems feasible:

1) Admin makes a change and commits to dev branch
2) Post commit hook sends email, requesting peer review
3) Second admin either approves the change or adds feedback
4) Once approved, the change is picked up by a cron script and
integrated into release branch

Now, where my complete lack of SVN skills show is that I don't know if
this is possible. Are there additional tags (META?) that can be added
to commits, that can make one of these scenarios possible? Are there
existing hook recipes, that someone knows of, that could help me along
the way? Any insight is appreciated.

-- 
--tucker