I don't know that I like the points being purely on achievement. You may have good leaders that don't like the region process. You may have good leaders that aren't in the top band because it's incredibly competitive. You may have great leaders that are quality musicians but not jumping through hoops to earn points.

If you want certain kids to be leaders start teaching them to be leaders so that they don't shy away from it. Don't be afraid when it's time for applications to come in to suggest to a few students they should consider trying out. Never keep a freshman from going through the process just because they don't have "enough points". They go through the process as a sophomore and sure, they aren't going to be drum major or section leader.... that year. But they see the process and what you are looking for in leaders, (by the questions you ask during the process), and they develop. I had a number of students who tried out for drum major as a sophomore who became a drum major as a senior.

Never back yourself into a corner. What if you implement a system and end up with only a few applicants that you really don't want but are stuck with because you eliminated others from applying.