Focusing on test scores over other aspects of the applicants is part of the problem of schools and companies creating these exams. There should be other diverse methods for evaluating students. By focusing so much on test scores, schools pick such students and thus tests have to be re-calibrated to measure the differences amongst students. Their top priority should be looking for a good future doctor and second is a good student.
For the sake of the conversation, let say nothing can be done to change the current culture of higher MCAT scores => better students => tougher exam => even higher MCAT scores => even better students. I don't believe the faith of certain low scorers to be set in stone (of course there are scores so low that they maybe beyond the help, I don't believe that point to be in the low 20s range). As long as the correct study methods are learning during medical school for classes and the correct board prep materials are used (we have more types of prep materials than in the past), then a person has a statistically better chance of passing their boards.
I had a friend who matched recently that got into my local MD with a 22 MCAT. He went through the local post-bacc program and passed it. The program prepped him very well and thus was able to pass all his boards. He also told me there were several classmates and people senior to him who have scores from 22-25 in the program. These ones who did pass the program all passed their boards (the USMLE step I and II). To be fair the program has a 50-70% pass rate, so it serves a a weeder too. However, if study methods are given and done correctly these students can pass. Medical schools have to teach a lot of students, so these individualized interventions are very hard or if they are done, they are done poorly.
Schools should look for a standardized way of evaluating students beyond the MCAT and GPA. This would lessen the extreme focus on test scores.
On a side note, by increase MCAT stats for DO schools doesn't help change the way they are perceived by PDs of residency programs. You still have the USLME which already does a good job of this (I think there is too much of a reliance on this exam too). The key to bridging the gap in this case is by standardizing clinical education across the board, which are on par with the LCME. However, even then, this separate but equal aspect won't be enough and integration into the LCME would be the best option.