I was thinking the same thing, that is, that the UI is the problem, the data model can pretty much model any situation but there is really no usable interface to it.
I'll also try to check out Ryan's code in the next week or two.
The package now tries to improve upon the existing UI. Its capabilities are limited to basic group creation, user assignment, and group permissioning, but I think it will be useful in many cases. There is some support for relational segment assignment.
