As for your first issue, abusive parents, this does not warrant blanket bans that jail innocent people. Not to mention abuse victims would be more likely to come forward in a more sexually open society.

What if the child becomes involved in sexual activity with an adult without the parents knowing about it, and the parents have a sex-negative reaction without respect for the consent of the activity. If only the law were changed, how many parents would then report the adult?

Under my proposal they could treat it as abuse. Much like the states with the "age of consent is 16 with parental consent" laws. It isn't ideal but it is better than what we have now.

And if the adult were reported, would the court then respect the opinion of the child or judge by the absence of parental permission?

The paedosexual adult would be charged, but depending on the circumstances it would change. If it is a case of deception where they were manipulating an otherwise consenting child who was unaware of the manipulation it would be more severe than if it was simply because the parents were anti-sexual.

What if the parents' judgment is clouded by the status of the adult involved? What if the adult is the dad's boss, and he can't risk losing his job, would it then take more for the parents to disallow the relationship? For the sake of argument, we could say that the child doesn't feel strongly for or against the sexual activity.

Just as with any other situation, other adults in the child's life could make reports. Other than that it is a crummy and rare situation. Nothing can be utopian.

Also I'm not so sure that regret and shame will vanish. Perhaps there will be cases of adult children having regret, and then blaming the parents.I think parents having openness about such subjects as sexual acitivity, and acceptance where it is due, is important in mitigating regret and emotional issues. That can exist with or without a 'parental permission law', and a 'parental permission law' can exist with or without parents having the mentioned behaviour. The law might, however, move public attitudes in a healthy way.

Of course future regret and shame will never vanish. It will lessen in intensity and quantity though. I regret and feel shameful about many past things, but it's whatever. No reason to dwell on it or care much. I remember when I regretted my childhood sexual activity and it was only because my parents and religion had told me it was bad. I am confident that with a more sexually open culture and upbringing the shame and regret people, even adults, feel for past sexual activity will reduce to nothing more than an occasional blip on a few people's lives.