The prod of a comment here helps, thanks.

I took the repaired patch and made a new bugfix branch.
Can confirm that it builds. Only testing issues are those
caused by expected changes in error messages.

Since this is a new feature and not just a bug fix, I'll
ask for some other opinions on it. Given that, it won't
go into the 4.1.2 release, but with positive opinions could
go into the next 4.2 release. We don't need a full TIP system
to develop Itcl, I don't think, but wise comments from multiple
users would help me have confidence the feature is sensible.