So I had an idea based on a number of the threads going through the forum recently (and not so recently) about customization and building your own 'decks and the like. It gave me a book idea I'd love to acquire/see:
A Customization/Construction Guide for all things Shadowrun. People are missing the rules to make your own spells, equipment, etc, especially since hide nor hair have been seen this edition. Putting all of these rules in a single book would make things much easier.
Now, this would never be Missions legal, but that's not my concern. My focus would be on building your own drones, armor, guns, spells, vehicles, 'decks, RCCs, buildings for all I care, etc. as well as modifying pre-existing pieces or your new ones. Consolidate some tables with all the current modifications out there, add some new things, give prices, times and what tests it takes to draw them up yourself, or to hire someone to do it for you (throw in modifier tables for equipment on hand, material quality, assistants or lack-there-of, etc.). Give a chapter of fluff about customizing your stuff in Shadowrun, about how the Megacorps discourage it and start voiding warranties and introducing countermeasures while skilled people jailbreak things and add aftermarket parts while talented 'runners build their own kit from scratch, literally making the bleeding edge in some cases. Get into the vehicles/drones and car culture, those magicians who develop new magics, maybe even a sidebar describing how to come up with balanced Adept Powers! The possibilities aren't endless, but close.
Also, just for the rules-lawyers out there, when you get to the first page of mechanics on building your own things, put in nice, big, bold, bright letters...
ALL CONTENT AT THIS POINT IS ONLY AVAILABLE AT THE GM'S DISCRETION.