EDIT: I think this is answered in section 6, actually. Thanks!
Very cool. And amazing that you got to speak to (the!) Gordon Plotkin about it.
Is there to be any support for differentiation at the datatype declaration level? Of course it's possible to represent all data in terms of Vector{N} and, in some circumstances, it may make sense to do so. But for a lot of programming tasks it is nicer to work with say, a Features struct instead. To put it another way, we have structs because we know that tuples alone just won't do.
If you'd like to discuss further, please PM me. 