Yeah, "tags" seems more like a narrative idea, best suited for foreground growth. You may check Block, Dodge, Parry to see how it can be implemented in Cairn hack. Some of those are more like modifiers, but some are really interesting:
https://lars1808.github.io/Block-Dodge-Parry-SRD/careers-and-skills
Finally! And I see that you've already mentioned things I wanted to suggest, such as simplification of "advanced weaponry", rules for more compatibility with Mothership and more tools for content generation. Maybe also expand on some optional sections from 1e, like "Tags"?
Other than that, it's really hard for me to suggest anything else. Monolith is already such a nice little, yet tight package. I'm very excited to see what 2e will look like!
P.S. Oh, and for quality of life - please add bookmarks to the PDF! This is a small detail, but it can greatly improve the experience of using the book.
