If you use that file your PrefPanes error will disappear and the "input devices customization" will 100% work again. It's the same identical CoreBrightness file you could obtain if you patch it yourself from your machine. I suggest only this time use that file, at the next Mojave beta 6 for sure they will update it and so then you will try the cbpatcher yourself.
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Still no dice. Ran the steps, didn't get any codesigning errors, rebooted twice and I am still having the same Preference Panes issues. Thanks.