I've got the mousetrap and you've got the venue. The Allamuchy scout camp property is the ideal place for a true MTB event. The trick in my opinion is to keep the actual race simple, challenging and doable for a wide range of riders. 3 or 4 classes maximum, no crazy prizes or swag and cheap entry fees. Keep the public input to a minimum because you can't please everyone. So my idea would be a 9 hour race with a start time right after sunrise. No lights needed, basic manual time keeping, and a lap that would take the average sport rider 60 minutes or so and the leg shavers 40 minutes to complete. Solo men, solo women, 2 person teams and SS. That's it.
I more or less agree with this with 1 addition. You need to announce it as early as possible. Our biggest issue in the past is that we announce too late and everyone has out-of-town plans already. Anyone with kids needs to figure out what to do the last week of summer because all the camps close. It's February 17th today, and we have all the kids signed up for camps because they fill up by March, and even then we're on a wait list for 1 of the weeks because it was full already. We already know what the whole summer looks like by mid-winter.
If you want to really make it happen it needs to be on the radar in January. Even as of today, a good portion of potential riders have vacation plans.