Not sure it needs more +1s, but to add to the “should it exist” my most enthusiastic YES. We’ve talked about this for ages and it’s something we discussed well before even RMarkdown existed. For various reasons in our ecosystem we never fully implemented it (sometimes I wonder if the existence of reST with some of its worst design and implementation decisions has hurt us more than helped in the long run, but I digress). But I think it’s unquestionably a needed idea, and now between MyST (that gives us some design freedom away from pure reST) and JupyterLab (that gives us better extensibility to explore UI ideas), we should go ahead.
I’ll dig deeper into the rest of the thread later, but I wanted to chime in about how happy it made me to stumble on this tonight 