Can these files and registry entries be added to an offline image? I don't want to have to sysprep and capture another image. I don't either. Passing SFC is just one of those things that makes me feel like I've done it right. It's a peace of mind thing basically. If it doesn't pass SFC it's going to be in the back of my mind constantly whispering "Psst. Hey. The image didn't pass SFC." to me.
Interesting. I'll definitely try it out. Didn't know a secure boot compatible theme patcher was out there. Thanks for the link @Intmd.