> The C (near-) subset of C++ is (modulo standard libraries) a starting point for this; just adding on templates for type system power (and not for other exotic uses) goes a long way.

In my experience, this is absolutely true. I wrote my own metaprogramming frontend for C and that's basically all you need. At this point, I consider the metaprogramming facilities of a language it's most important feature, by far. Everything else is pretty much superfluous by comparison