Seems like you could get at least 75% of the way there in a single day using Inkscape as the drawing platform, depending on what else needs to happen with workflow (like scripting to add another page blank, which seems like it's less of an "Inkscape page" and more of a "rectangle I can write on & export as PDF", with the PDF export of a selected area doable as-is but maybe adding a specifically-sized rectangle where you want it is worth scripting) or tablet / writing operations. LO Draw would also be a candidate.

If you want your grid to be even more interesting, integrate Eagle Mode around it (i.e. install and skim the Eagle Mode docs) for harnessing the powerful & more or less universal taxonomy of a filesystem. You'd have multiple levels of zoom & pan workspaces there, since it will preview the PDFs as you zoom to their location.

So, if you want to wait for something to fit the spec to your inner-critic's liking, I guess that's one thing. But if you could get most of the way toward what you want within a day...even though it wouldn't be perfect...would that be worth trying?

There's also a Patreon for Inkscape development IIRC...