So far I think I'm going with:

Hat
Shirt
Pants
Shoes
Gloves
Coat (over other shirt, for jackets, vests, robes, or armor over clothing)
Item equipped in Right hand
Item equipped in Left hand
Cape
Face Accessory (eyewear, masks, etc)

So 10 slots total... I guess that's a good even number. I'll also have glove items that can be worn as a single glove, or at least a way to hide one glove.

I didn't like the idea of having a left hand and right hand slot because then you need to collect two glove items just to wear two gloves... Which seems like too much work just to wear a matching pair of gloves.

edit: I'm also considering what Caldenfor mentioned, and just having the 5 main slots be used for stats. But I think I'll figure that out through some testing and just seeing what works.

I like the minigame of finding/crafting/buying an outfit based on what I want my character to do, but too often the gear becomes the character. It becomes irresponsible to wear certain equipment, regardless of your own wishes, because the bonuses or properties lead to a "best set" situation. Conan beats faces on a regular basis while wearing a loincloth and wielding a length of chain, because he's rad. I always run into trouble in Fallout and Elder Scrolls games because I really want to play the game dressed in the kind of clothing that a person would wear if they were going to be walking thousands of miles and conversing with strangers most of the time, but the game railroads me into wearing a gold-engraved glowing robot suit down to the corner store, since I have to always be on the lookout for monsters and brigands and headhunters that will travel for days or ignore their own needs in order to take a crack at me.

You mentioned Final Fantasy Tactics, and my favorite part of that game is in the beginning, before your team consists exclusively of unique, historically significant heroes. I like having a team of cookie-cutter dudes, wearing standard-issue gear, and I consider the assignation of a rare sword or fancy armor to be a privilege conferred upon distinguished members of the team. Especially when I have a whole squad or platoon to manage, I don't want to spend hours of gameplay time playing dress-up with my dolls.

So go ahead and include lots of equipment slots, but don't require too much micromanagement there. Let the little guys wear their work clothes, and only make me go into that menu when I want to deploy some sort of wearable force multiplier to the battlefield.

As an aside, I'd put Dwarf Fortress at the top of the list for convoluted gear and clothing, since it factors everything from your cape to your helmet to your underpants into damage calculations, but it also features a military management system that allows you to set rules like, "All axedwarves in the third squad will wear steel chainmail, the best metal helmet they can find, a blue cape and bronze gauntlets except for the squad leader, who gets this artifact iron breastplate with the picture of cheese on it," which removes much of the tedium of dragging gear into slots without restricting my ability to customize my little dudes.