I have found a workaround that worked on Windows 7 after a windows update killed my function keys.There's no guarantee that this will work the same on 10, but it might be worth a shot for those still having issues. These were the steps I tried that ultimately got my keyboard fully working again.
First step, as established in earlier posts, is to get clean Boot Camp drivers from the apple website. Find the appropriate version for your mac and download the whole package. The key, at a later stage, becomes manually managing some of the OTHER drivers. I didn't have ANY luck running the all-in-one patch. More to come on that in a minute.
The first main thing I noticed in relation to the keyboard was that my computer was still "recognizing" the keyboard, but not as an Apple keyboard. It was being listed as an HID device. This meant that when I tried to delete and repair the keyboard, it was stuck in some limbo realm. So I uninstalled the keyboard on the MAC side of my computer. Pain in the butt to have to use virtual keyboards on both, but at least that freed up my keyboard to pair on the PC half as a clean install.
When I attempted to run the automatic repair on windows, certain drivers weren't installing properly. The ones that stood out were Bluetooth HID device (bad keyboard link), the Apple Broadcom Built-In Bluetooth device driver software, and the Apple Bluetooth Enabler. So, I went to uninstall or change a program and deleted the windows driver packages linked to these error messages. Then, one by one, I manually went into the Boot Camp file brought over from the Mac. I first manually reinstalled the drivers AppleBluetoothBroadcomInstaller and AppleBluetoothEnablerInstaller, This caused the keyboard section to return to my bootcamp menu and made my keyboard discoverable and linkable to my PC. However, it kept dropping and asking to reconnect. I then deleted the AppleKeyboard driver from programs and manually reinstalled just that component AFTER reinstalling the abovementioned Bluetooth drivers. This restored the keyboard typing function and seemed to properly pair it. It was now listed as a rechargable keyboard by Apple under devices. Good step.
The final step I noticed was that the little bootcamp icon was missing from my dash, so I went into Program files/Bootcamp/BootCamp.exe and clicked it so it world start running again. THIS was the step that restored the function keys to full use.
I hope that this workaround helps someone else!