I was looking for a quite robust function to convert tibble to matrix with handling of rownames. I created this script that I would enjoy in dplyr/tidyr libraries as user
You might be interested in the tbl_cube format, which I think is best described as being to arrays as tibbles are to data frames. @mdsumner and I have talked about them a bit with respect to their tidync package, but I don't know how much of a priority tbl_cube development is for dplyr.