I think your motivation is very good.
It would certainly be a great service to offer a place where students who are studying on their own can meet others, plan for and review practice tests, and hear about strategies. That community aspect of a prep course is nice for people studying on their own. Also, people might share materials; you might be able to find a few people who would donate their used prep course materials (if it's legal).
Those who have taken the MCAT have the great advantage of experience with timing, accuracy of practice test scores, strategies for making it through the day, being able to share idiosyncracies about the local test center, etc.. You can also really help people save time by focusing their studying on the important topics and targeting the stuff that often appears on the test.