I am actively using keyfiles for non-boot partitions and files (containers?), but I am wanting to bring this into the full system with a boot partition containing my OS (Windows or Linux). However, I really like the security keyfiles offer against bruteforcing, and commonly employ 25 1MB files as keyfiles (essentially a 25 million character password). Right now, I leave the OS unencrypted but store all the important files in the container and this allows me to use Keyfiles.
I don't want to wipe and reboot if I don't have the option, and the docs fail to explicitly say whether it be available or not.