I had a brain when I was 16 so I didn't make any choices that will loom over my head forever.
None of what you say makes any sense, your leaked nude at 16 isn't going to affect your life forever, so your ex uploads it on some porn site? First of all you can get it taken down, it's very easy to do since revenge porn is illegal now, second, even if you couldn't, there are so many porn videos that the chances of anyone randomly coming across your porn video or nude picture on a site are miniscule. Secondly, the pictures would not be passed on and distributed for the rest of your life, since it is ILLEGAL and people would not be sharing them if you instructed them to take it down. It couldn't get to a point where it got completely out of hand and there was no way to erase it, since you aren't Paris Hilton so it won't be distributed on a significant scale where it 'looms over your life forever'.
Your idea that if you do something bad at 16, you shouldn't have to pay for it for te rest of your life is incredibly stupid, however. 16 year olds are not 7 year olds, they can legally get married, have sex and so on. If a 16 year old murders someone, they will be prosecuted and they won't be let off just because 'they are only 16, they just made a bad decision'. Stop infantalizing teenagers, if they are mature enough for sexting then they are mature enough to handle the consequences, and if you don't think so, then surely you should advocate making it illegal for teenagers to send nudes of themselves to anyone. People like you constantly come out with these insane statements, everybody is allowed to do whatever they want, teenagers should be having sex etc, it's none of anybody's business, but they shouldn't be held accountable for their actions because they are babies. Make up your mind.
This is the biggest problem of this generation, everybody thinks they are entitled to do whatever they want and when they suffer the consequences of their stupidity, no one is allowed to call them out on it, we all have to sit in a circle and hold their hands. No.