Beyond matrices and vectors, it would be nice to have generalized (typed) tensors. What you can do with matrices alone is really somewhat limited.
https://github.com/deepmind/tensor_annotations seems promising. I've developed a mypy plugin for pytorch that does similarly off of the "Named Tensor" dynamic feature (which isn't well supported yet), but haven't released it yet.
I'm also excited by the ways in which including this in some sort of "first-class" way could make tensor semantics simpler, which I'm assuming xarray allows? Many of the operations enabled by http://nlp.seas.harvard.edu/NamedTensor are quite nice and similar ideas can let you write more generic code (ie. code that works automatically for on tensors with and without a batch dimension)