Since we didn't need to backport subversion I can only give a general annswer:
We are using an internal reprepro, it's a nice option to get your own software easily distributed in your company across multiple hosts and even provides gpg signed packages (if configured to).
Of course you need to dive into the depths of debian package development (at times) but it quickly pays of once you have basic steps documented.
Packages already in upstream for which you only need a newer/specific version are very easy to pull in (most of the time). In 90% percent of the cases you can simply get the source and copy the
debian directory inside so after a
dpkg-builpackage (look up the required options in the manpage) you simply upload it to your repository and can then simply
apt-get install the package.
However the documentation isn't exactly colorfull so you may run into problems depending on your knowledge, overall I can say it helped us a lot streamlining our systems since we now have a central place to pull (internal) updates from. You can even configure it tu regularly (or manually) pull updates from upstream repositories and can even have multiple distributions which you can use for internal testing since you probably don't want untested packages from backports.org or the volattile repository to be installed on your server without prior testing.