Since it has been FOREVER since I've played Morrowind, I don't know the answer to this.

Is there a point in combining an Armor skill with Unarmored? I know that you can wear clothing and armor at the same time - example you can wear robes over Heavy Armor. Would there be a point to this at all? Or would the robes end up being aesthetic more than anything, only the armor rating of the armor would be counted, and Unarmored would end up being a waste of a skill choice?

Unarmored is applied only to parts of the body which can be covered by armor. The applicable slots are hands, arms/shoulders, head, torso, legs, feet, and shield. If you don't have armor in one of these slots, it gets covered by your Unarmored skill. Other wearable slots (robe, skirt, amulet, rings) are not affected by Unarmored.

if you think in terms of pure efficiency, then armor + unarmored is unseless, as you can equip all the clothing along with armor (except for shoes and gloves).
oblivion improved that, disallowing clothing when wearing armor (nice balancing idea for an MW-mod, now that i think about it)

if you think in terms of character diversity...
i just hate ALL of the helmets. won't ever again equip one (is there a mod making them invisible?)
then look at almalexia or vivec; they wear SOME armor parts, and are "naked" otherwise.
that could be a nice style for a main character who is very powerful (by the time you meet with them, you probably already are).
or just a conan fighter with boots and gloves.
etc. etc.

The Heavy and Medium Armor skills, the Light Armor skill, and Unarmored affect different Attributes. It sometimes makes sense to wear one different piece from the rest of the set, to boost that other Attribute; my current character wears mostly a mix of Light and Medium, with no helmet.

None of my characters have ever worn a helmet. On top of that many of my warrior characters haven't worn pauldrons either. So I always take one of the three armor skills plus unarmored.

Unarmored rocks. I find you can carry more loot without having to don any armor. Walk softly and carry a big stick.
Sometimes though, like with my current character, I will wear Cuirass of the Savior's Hide for the resist magic constant effect, but no other armor, and both light and unarmored get built up through use.
I would say, there is future benefit, because if you wanted to eventually get into another armor type later in your game, when you can carry more, maybe through fortify strength constant effect clothing, and armor or something, you can gradually work on both unarmored and any other armor type you want....and eventually sport full Daedric and still carry a reasonable amount of loot. Not my style, but your mileage may vary.