I was pointed to this article about Charlie Munger by @paltman who kindly said he thought of me when he read it.
The article talks about Munger as an expert generalist, a term it attributes to Orit Gadiesh.
The term expert generalist is, I think, a pretty good attempt to describe what I've been talking about here. The "expert" adequately highlights that we're not just talking about a jack-of-all trades generalist but the "generalist" contrasts with a specialist in just one area.
I Googled around and there are a few articles talking about the expert generalist in this sense.