My main issue with your argument here is that you rely too much on historical precedent to determine right and wrong. You often appeal to what *used* to be acceptable, and use that as a reason for why it should be okay today. Maybe I’m misreading it, but that’s how your argument appears.
My other issue is that you never address the moral agency and cognitive ability of a child or teenager. The human brain does not finish forming until around 25 years old. This is why we often have “juvenile” criminal records, that get sealed up when you turn a certain age. We do not hold children fully accountable for their actions, and that is because of their immaturity, lack of experience in the world, and not having fully formed cognition. This is why children are not allowed to sign contracts. For these same reasons, it should not be legally, morally or socially acceptable for a child or teenager to enter into marriage with an adult. They are entering into a life long arrangement and commitment without knowing what they’re truly getting themselves into. A marriage between an adult man and an adolescent girl is an inherently unbalanced relationship because of the reasons I’ve outlined above.
It seems to me that in this paper you’re starting with a conclusion in mind (that child marriage is okay), and walking your way back from there and trying to figure out how you can *make* it okay, rather than approaching the subject from a truly objective place and sorting it out. But that’s just my opinion.