In regard to Discover, why not make your options cards that are NOT in your deck?
The whole point to using Discover is to discover something you haven't seen before. If it is in your deck, you've obviously seen it...for example, Primordial Glyph should not give me another Primordial Glyph that I can use to power my Mana Wyrm.
Primordial Glyph should recognize, "There are 2 glyps here; Glyph can't be discovered." Therefore, exposing you to spells/minions/options you might not have otherwise known existed.
Basically, Discover mechanics should stick to the "only 2 copies per deck" rule.