Im a master armorsmith and enchanter. I am currently running around in Light Dragon Armor, but the coolest looking armor is the nightingale leather. So why cant I make my own set so I can enchant it with what I want?

Because it's special armor gifted to you by...

Deal with the greater damage it takes and just roam around like a bad-ass.

Same reason you can't make ebony mail

Special armors and weapons obtained through quests can't be created. That's why they are special.