I finally got a chance to read the UA Bladesinger. I love it.
I like the armorless flavor. The Int+Dex+Mage Armor is sweet.
At the same time, I want a background-feat "Fighting Style" that grants at-will Mage Armor. This armor can appear in any armor style the player wishes (plate, cloth, whatever), or as an invisible force. The "ancient elves" traditionally make this Mage Armor appear as if a silky fine mithral chain mesh − and this spell is actually what "Elven Chain" is. Anyone, especially a Wizard (not yet a Bladesinger), Fighter (not yet Eldritch Knight or Psi Warrior), Rogue (not yet a Trickster) can take this "Fighting Style" for their background feat at level 1.
Did any character optimizers look at the bonus action attack at level 14? Is this a good feature at this level? Are there any interesting combos with this?