> Thanks for your feedback. Do you think these two need to be treated as separate modules, i.e. they should be *two* papers, or can they be considered together as one, i.e. i.e. one paper covering both?

That's up to you, but don't forget that a paper either is accepted as it is or sent for revision; and it wouldn't be the first time that an author decided to split his proposals up into multiple papers (compare with the excellent work done by Alisdair Meredith to examine which deprecated parts of the library should be removed piece by piece). While I'm far from a deep expert on mdspan and view_interface, they seem like sufficiently different beasts to me that you might be able to get better detail on both motivation and the specifics of your proposal if each were given their own space to be talked about - after all, access to mdspan is multidimensional so will have a very different interface from access to a generic view_interface.

But that's just my 2c - your mileage may vary as you get deeper into your proposal.