Win10 Bootcamp on 2016 15" MBP woes (I think it's due to macOS not copying over ISO contents to internal partition)
Moved my win10 ISO onto someone else's 2013 MBP, created a bootable USB thumb drive there, popped it back into my laptop and copied over $WinPEDriver$ and BootCamp from WindowsSupport folder downloaded on my machine over it. Was able to install onto the existing bootcamp partition and all went well. :)