There are already units libraries for C++ that go further than this, including dimension checking (e.g. a velocity type divided by a time type gives an accelera

There are already units libraries for C++ that go further than this, including dimension checking (e.g. a velocity type divided by a time type gives an acceleration typed result with correct units). This extension idea doesn't seem to offer much over existing library solutions, though it might make writing those libraries a bit easier.