I do not particularly desire preteens or "tweens," but I wouldn't turn them down. Plus I have said for a while we need a Generations pack to make other ages more fulfilling to play.
What I really want is for teens to be proper kids still. Yes, they need teen specific stuff, too, but it is pretty ridiculous that they cannot do anything childish when they are still technically children. Some teens are fairly childish, and do not stay that way the rest of their lives like when giving them the trait. Right now they really are YAs with high school instead of the bridge between childhood and adulthood.
I realize this might be what you may want the preteen to be, OP, but I think there is room for both here. I specifically want it for teens due to my own personal experiences.
Obviously elders need more, and every stage could use a dose of uniqueness if they can get it.