@Mitch OK but those two things are quite close, aren't they? (Of course it's not a term that most people actively use, but surely you will know that I don't care about that.)
The first thing I think of when you say commonwealth is the Commonwealth, which could be that of Cromwell or that of Elizabeth II.
(what you call my two closely related sense, I think are very different and would not confuse). Also I don't associate 'common weal' at all with the Cromwellian Commonwealth or any state called a commonwealth.
To me 'the common weal' is an abstract concept for public goods, and 'commonwealth' is a label for a particular kind of governmental system.
English Language & Usage: Multi-Layer…
English Language & Usage: Multi-Layer…