First of all, that is NOT a normal Calibre Library structure you show
Calibre has it's own filing.
66 different fonts
Why not use 66 Stylesheets (with matching OPF files listing the current fonts)?
Or K.I.S.S.
Make 66 font sets and use a common file name so the OPF and CSS stay the same.
Font1.TTF
Font2.TTF
...
then use Tweak EPUB and switch out fontfiles
If you still want to do the Library way:
Calibre does have a 'Copy to Library'
You create additional Libraries (with the same structure) , then select books: right click: copy to library