Piaget believed that after about age 12 kids can understand abstract concepts and reason logically. But as you stated, today's youth do not mature as soon as in the past.
The debate on this issue (pedophilia) will end up being about "age of consent". And many ideas and considerations, including yours and the other response poster who favored age 18, will all be tossed on the table for discussion by the state. It will also involve age of consent (without parent involvement) for vaccines, abortions, birth control, etc. as the battles rage.