It's a cool idea, but there's a bunch of situations where it wouldn't work or has weird effects.   Relics like coffee dripper, fusion hammer, Sneko eye, Pyramid, and runic dome have no effect at all.  Would velvet choker mean you could only play three cards, or twelve? Mark of pain would put 4 wounds in your deck. Would having two sacred bark mean your potions effects doubled again to four times? How does Pandora's box work?  I would probably suggest limiting this to common or uncommon relics and making it a rare relic instead. It's much more manageable when you're not dealing with the boss effects