This is an interesting subject and one that I've heard brought up over many years by Clubs for the Associations they are members of to look into but had never panned out.
Obviously you'll need to know if there is an interest/need for such a program and that will take a bit of time to conduct your survey.
I for one would support a program of this nature but feel that any cost should be covered by the event host. For those of you that don't know me, I have been the Chairman/Organizer of the PA Jeeps Annual Jeep Show for the past eight years and we have been dealing with event insurance for 14 years. The biggest problem with liability insurance for an event like ours had been finding a broker that understands clearly what is going on and NOT being fearful of how things are/will be monitored. When it's stated that the event is run by and monitored by "volunteers" with said Club/Organization they are understanding there is NO professionalism, proper judgement, when a clear written authority is not involved.
Yes, our event continues each year and we have had liability coverage and have been fortunate to find a broker with a reasonable cost knowing that there are 5,000+ people in attendance. However, our event is NOT on public land (rented business facility), nor is it a "trail ride" type of event that if it where would most likely send the cost beyond the event continuing.
Other Club events held here in Pennsylvania that are trail ride oriented are held at the Rausch Creek Off Road Park. To my understanding that insurance is covered under the Park's umbrella which in turn is within the registration fee for said event.
If UNITED where to acquire an insurance broker that can/will cover liability for Club events at a lower cost based on each individual event and its happenings I would like to hear of it and discuss it. But I don't think the UNITED membership as a whole should share that cost. Consider how many members of UNITED and its Associations actually are active at the thousands of events is most likely needed and even then I'm not convinced that a "cross-the-board" fee added to membership would go over very well in these times. I could be wrong, but time, surveys, polls, and serious discussion could/may change that.
Keep this subject going further...You are on to something that may very well be beneficial to EVERYONE within the OHV community.