Okay, brain blast, I just had a thought for a stretch goal that might not be as much of a hassle as canon characters, but could exist in the same vein: Letters from the Inner Sphere.
Everyone gets to write a short, in-character letter—be it a report to a superior, a check-in to the folks back home from the front lines, a formal business complaint to QuickScell, or whatever. Those letters get published under the same "it's all just perspective and half-truths, plus the occasional prankster" policy as the sourcebooks. Authors can then choose letters to canonize, use as inspiration, or even cite excerpts as is convenient at the time, giving CGL a more "pick and choose" approach with no obligation to actually use every letter. And for the rest of us? Well, backers at such and such tier and above may receive a randomly-chosen letter as part of their fulfillment, plus a PDF and/or EPUB/MOBI compilation of all letters to revel in the fluff, the implied stories, and the occasional spot of utter chaos.