I'd love it if we were able to buy vanity items (hair, eyes, noses, mouths, colors, etc.) from the subscriber-only pool. I did subscribe for my first month at $14.95, but I've achieved most of my goals and am largely logging in for social reasons now, and for less time. As a result, looking good still matters to me and, while it's not quite enough to merit a subscription, I'd still be willing to pay a little extra for the privilege.
I realize that the subscriber vanity options/clothing are there to reward said subscribers, but I don't feel that allowing the items for individual purchase would undercut the benefits of subscriptions. As a subscriber, I change clothes and coloring almost daily because I have access to almost everything; as a non-subscriber, I'd be limited to only the basic options and what I'd purchased in the cash store.
Essentially what I'm saying is that the things I'm interested in buying are not currently for sale, so there's still an unexplored avenue of monetization that fits within the current payment model.