I only have a couple of things in /opt/ and some manually installed fonts, and vim plugins in my home. Everything else that I don't use often lives in the original cloned git repo in /home/projects and never really gets installed.

Of course the process breaks down for a large amount of packets, but I've never been in that situation. In part because the official repo is already large, and in part because I like minimalism.

If that even became an issue, I would manage a personal set of pkgbuild probably.