GURPS really could use a 'setting generator' app that pulls in all the appropriate rules from the various GURPS books, and generates a clean PDF just for your setting, with a section you can type setting notes into. I'm making these kind of books for my settings. Unfortunately, I can't share it because it has copyrighted material in it, but the general layout is:
Introduction -- What the setting is, what you need to play, and what assumptions are in play rules-wise.
Character Creation -- a list of races and occupations, and specific rules about character creation (one 250 point occupation, 100 points for race, 200 points to customise, for example)
Traits -- A list of valid traits for the setting, plus any modifications from GURPS baseline.
Modifiers -- A list of valid modifiers for the setting, with any modifications noted.
Skills -- A list of valid skills for the setting with any modifications noted.
Magick -- A list of valid spells for the setting, with any modifications noted, plus the system (RPM, GURPS Magick, Sorcery, etc).
Psionics -- A list of valid psi powers for the setting, with any modifications noted.
Wealth, Status, and Equipment -- A gathering of rules around money, and the setting's gear book. This could be broken out into its own book.
House Rules and Optional Rules -- A list of rules used in the game. A collection of all the special rules in use in the game, taken from both Campaigns and any Pyramids.
For my GURPS: Rifts game, there are also notes from Rifters (Palladium's version of Pyramid) and occupational templates for things like Juicers (Chemically augmented supersoldiers), Crazies (cybernetic warriors with brain implants that ... make them go crazy), and Deadboys (faceless armoured soldiers representing a despotic human-supremacist government. Their helmets are all stylised skulls...).
Problem is that I'm not sure how SJGames would be able to write this app. You'd need to make sure the player had the necessary PDFs on hand to generate it, and I'm sure that SJGames would want to make sure those are legit PDFs.