10 isn't enough for me, at least. I have all 10 of my slots taken by different versions of my avatar, and I use each one. Problem is, what about when I do an RP? I have to re-design the character each time I want to use it. In my opinion, it doesn't even have to be a default feature. Someone could make an add-on that allows this, although I'm not sure it would be possible to do exactly what I have in mind.