Creepy OP.
Western teenagers generally start having sex on average when they are 16-16.5 years old, this is fairly stable across various countries. So 16 means almost half of teenagers start having sex when they are underage. This is the main reason we have the age of consent at 15 in my country - it is simply more realistic and does not criminalize so many relationships. Still, 15 is a bit young to have sex with an adult (you mature fast in that age, so a year means a real difference). So if you are going to have one age of consent for all I think 16 is the most reasonale, but can live with 15.
An alternative is the 10 year+ rule for under 18s (you can have legal sex with minors above, say 14, if you are less than 10 years older than them), but that is artificial and guys in their 20s can prey on teenagers as well as older men (and older teens on young teens), so it is generally not a sensible idea.
Good proposal.
