You're talking over my head, but thought I would pass along a (possibly) related thought.
Several players are using 4k TVs which works fine for 3D graphics, but text becomes too small to read comfortably. While I'm not sure what your Font Metrics is meant for, creating something that literally enlarges entire panels displayed and/or the fonts used in said panels would probably be greatly appreciated. Note that I'm referring to all of the non-Chat related text.
The same exact situation exists with Inventory item icons needing to be enlarged as well. Here however their is a finite limit based on the size of the icons and no way to replace them with a scalable solution.
I realize in both cases enlargement past a certain point becomes so jagged as to be visually unappealing - if not downright useless - but this niche isn't getting fulfilled by SSG or modders to date.