Yeah basically use any enchantment you could normally use on a weapon for gauntlets, I think the highest one could get unarmed damage with the fortify unarmed damage is about 40 or so, that is fairly useless unless you're lower level, Deathlords and such won't even notice it.
You could always use the restoration potion glitch to make the unarmed damage higher. On one character I have those boneclaw rings from Dawnguard enchanted with +150 unarmed damage. Playing on Expert/Master this is almost the perfect amount of damage, maybe slightly too much but definitively not overpowered.
But yeah, I like your idea with the elemental enchantments. Flaming fists would be interesting.