Craftable chainmail, saddles & elytra.
Recipes where copper may replace iron for the same results: shield, tripwire hook, ...
Insta-grass 'cause this ain't Waitcraft, and face it - you're drowning in wheat seeds.
Quickly revert to ores using ingot + cobblestone:
So to be frank, I'm really not a fan of Minecraft's enchantment system.
IMO, it'd be cool to just have enchantment tables be like crafting tables,
so you'd simply have, for instance,
a recipe like this for Silk Touch.
And just come up with custom recipes for all the enchanted books in the game.