My personal opinion (which you mention in your opening sentence) is that your transcript is evidence enough of your upward trend and capabilities within your major. That's what the transcript is for. It doesn't sound excusatory, but it's maybe not necessary. I think most people address significant factors that contribute to a lower GPA if they do an addendum...like: yes, my GPA is 3.1, but in addition to full time school, I worked 60 hours a week to support my family of 7 younger brothers b/c my parents died in a car crash without leaving us a dime, so, all things considered, a 3.1 is pretty damn good in that circumstance.
Plus, we'll all be taking classes in law school that are required but not necessarily in our interested area of the law...what are you saying, then, that you'll only excel in courses that specifically support your concentration and not in the base curriculum, some being courses in which you may have no interest?