Hi Tim,
That does sound like a challenging piece
You are correct that Notation Composer does not currently have the capability to have different meters for different staves (though it is on the "wish list").
Perhaps you could post here whatever workaround you come up with. We've only had a couple of requests for such a feature, but there may be others who simply haven't asked, and who would benefit from your insight and wisdom
Thanks!
Sherry