Cool proposal! I've found this idea is both challenging and helping to grow. I've been working with course for a month and reached the Values Assessment so far. And as many other buyers have noticed (Leo also emphasized this problem) - motivation and emotion problems (inner demons) are getting worse with every new step towards a discovery of Purpose. The mastermind group may become a really great motivator!
Personally, I love plans, time-management and discipline (all the bureaucratic stuff =), so can help other members to fight procrastination while doing the course and getting the result, but I can struggle if the schedule will not be solid =) So, working together may be difficult but, indeed, worthwhile.
Can start on 1st July, I'm from St.Petersburg, Russia, my timezone is close to Finland