I just equiped my dark fairy pet and it is realy close to the ground so close you can't even notice it unless you know you equiped it. I think this is a bug.
card that did like +1 damage and was only 1 training point to learn, and then there is a shield card that does +20 damage for 1 training point, everyone would learn the better card. The more cards that are created, the more likely there is already a better of its kind, or it is just a duplicate. Also doing this will just be the same creatures of every card already created, you said we would choose from different animals like snow serpet and fire elf, etc. Those have already been created, why create them again.
No need for this but if you didnt know this tip that is on the basic track of your idea is you can use the cards Keen Eyes or Tough to create your own treasure cards, by using the keen eyes or tough cards on the card you want to be created it will transform the keen eyes/tough treasure card to the one you selected.