Ohhh i love this arcana system, cant wait to try it out, and because you mentioned persona, i cant stop myself from thinking that it is really similar to the personas itself with their own weaknesses and spells, except you cannot change during battle, which sounds really fun!
theres just one small issue i see, and thats the way you access the class change menu, seems like you gotta go to inventory>key items>arcana mirror > change arcana, i think it would be way better to get a specilised button to instantly open it.
Aside from that, i really like the new turn crystals system, really need to tey it out and find a way to exploit it! :p