> put each class into its own header/source file pair (a great way to explode your build times!)
Is that really sufficient to explode build times on its own? Especially if you're just using the more basic C++ features (no template (ab)use in particular).
Not at all, you can write in the C subset that C++ supports and anti-C++ folks will still complain.
Meanwhile the C builds done in UNIX workstations (Aix, Solaris, HP-UX) for our applications back in 2000, were taking about 1 hour per deployment target, hardly blazing fast.