Even though stack and concatenate are nice for combining arrays, sometimes they don't fit the data I have or require a significant amount of work to use. For instance, combining blocks of different data. In cases like these, it would be nice to be able to use array assignment. While it is true that dask creates graphs of pure operations (with few exceptions) and assignment is unpure, one could imagine creating an array-like object that translates assignments into slicing and stacking/concatenating. This would allow a user to make use of a __setitem__-like syntax, but result in creating a new dask array (or potentially modifying the graph of the existing one) so the net result behaves like assignment while remaining pure.