I can't really comment from the point of view of having a teenager who was "APed" as a baby/kid because my 15 year old was not with us yet when he was younger. However, I was raised in a household in which nursing, cosleeping, etc. were the norm, so I can tell you a bit about my sleeping experiences growing up.
When I was a baby, I slept in bed with my parents. I self-weaned earlier than all of my siblings (I think around 9-16 months) because my mom was pregnant, and I didn't like the taste of her milk anymore. As the bed got more crowded with each new sibling, which happened sometime during our toddler or preschool years (we're all three years apart except for my younger brother who is 18 months younger than I am), my parents moved us onto small cots by the side of their bed.
Eventually as each of us grew out of our cots, we moved out of our parent's room (my brother was the latest to move out...it took him until he was about 9, while I think it took the rest of us only a few months from the time we moved out of my parent's bed). Once we left my parent's room, we would often sleep in the same bed with each other. I was the third child, so my older sisters often would let me cuddle with them, but I wanted my space at night by the time I was about 7 or 8.
My mom is an on-the-move-all-the-time personality, and her older kids never napped. She thought something was wrong with me when I came along because I was a sleepy child and was constantly falling asleep wherever we might go. I was well-known for waking up from long naps and sneaking off to crawl under the table for another nap. I've been that way my whole life.
As a teenager, there were days when I would sleep in until noon (teens' biological clocks are different than adults and cause more late nights and late mornings), take a nap again from 5-8p.m., and then get up and hang until 1 or 2 a.m. As an adult, I sleep more than most folks. My wife has gotten used to covering for me while I take a long (2-3 hour) afternoon nap at least once or twice a week.
All the kids in my family had different sleeping habits when we were children, and all of us turned out differently. I was the only sleepy child and am the only sleep adult.
In terms of independence, I am by nature a very independent person, and if anything, I probably stepped my feet out in front of myself before I was ready. My younger brother who moved out of my parent's room when he was 9, on the other hand, has always been a slow-to-step-out personality from the time he was born. This translated, as you can see by the above information, into our sleeping habits. I don't think it's probable that any of that could have been changed by my parents doing the sleep thing differently. We were all treated the same, and we all ended up with different teenage and adult sleeping habits. What I can say is that the way our parents parented us at night reaffirmed for us that we were loved and that we could depend on our parents to meet our needs...even the emotional ones.
As for my 15 year old, he still needs lots of sleep but resists it for as long as he can just like younger kids...
I'm pro-adoption reform, but not anti-adoption.