In my opinion (I'm a young adult too, and exactly one foot shorter than you Seabody), Sim me is too tall, and should be (slightly) shorter than the teen Sims, because I'm 5' and am shorter than most real life teens. So I'm with you on the height adjuster.
What I would really love to see back on Sims 3 is children, grown-up childish, inapproprate and party animal Sims jumping on the couches and the beds.
I think it would be cool if you can aim the slides to the pool, and have Sims use the slides to slide down the swimming pool (Sims of all ages). Also, I don't understand why childish teens and adults can't build sandcastles in the sand, or play on the playground. I'm a real life young adult with the childish trait and I still enjoy playing on the playground.
It doesn't have to be a waterside necessary, just a normal slide (the player) can aim at the pool using build/buy mode, and the Sims can slide down it. Also, I'd like to see Sims (mostly a interaction enjoyed, by the children, teens, and adults that are either/or childish, inappropriate and party animals), "CANNON BALL" into the pool. Maybe they can yell "CANNON BALL" in Simlish, splash the people around them, and possibly offend the high maintenance (snobs), freak out and scare the hydrophobes, cowards and neurotic Sims, and have the children and teens of all traits, as well as the YA-Elders that are childish, inappropriate, and/or party animals, get a happy moodlet, and fiendishly delight the mean spirited and evil Sims. Snobs can get some sort of moodlet where they're irritated or their hair gets all messed up from the moodlet.
Also with Swimming, I'd like to see a "too cold" moodlet when they come out of the water.