For 12.2 we're making an entirely new Builder, and it should indeed be possible to make it. Do you have a concrete example on a crystal to use (and perhaps a reference showing that it makes sense as a "ribbon", and how to define it), then I can demonstrate it perhaps.
You can already very easily build e.g. graphene and B-N or another graphene-like structure (i.e. A-B in a hexagonal structure).