Thanks for this input. I agree that fixed-dimension modules are useful, and indeed there already is a Mat module and I believe Vec is planned. However, a uniform n-dimensional Array type is still useful. For instance, one may want to take slices of it along one or more dimensions, which may reduce the dimensionality in dynamic (i.e. only known at runtime) ways. Or one can increase dimensionality by grouping etc.
While I admit that true dynamic dimensionality is probably rather rare, I would say it’s quite common to freely manipulate the shape and dimensionality of generic arrays in numerical computing. If one later wants to index the result, it would be a bit unnatural to have to resort to specialized modules whenever it happens to be 1,2,3-dimensional IMO.