When they're on sale, I'd have to spend more than 8,750 gold per character to make an account-wide unlock worthwhile. Regular price, 17,500 gold per character. To use one of the Outfit Change Token I've accumulated, I'd have to spend more than 70,000 gold on a single outfit change. I'm just not spending that kind of gold at the Outfit Station, which is why it doesn't make much of a different whether it's per character or per account.
Even if you were running a site like ESO Fashion, it's probably more economical to use gold to outfit change a single character than to buy more slots.
So I really don't see why everyone's been worked up for a year now on this. Outfit slots are like the most optional purchase of optional purchases. Additional character outfit slots are just there as a convenience if you absolutely have to have it, and like I've said before, they're priced to reflect the very low demand ZOS predicted for them. 1500 crowns apiece was the only way to give it any long-term value outside of opinion.