A couple of comments, firstly with respect to an annual event. A great idea but let me share something strictly between you and me. I say that because I'm about to completely contradict myself on the importance of membership growth.
My grandson and I attended Big EARS in 2014 and a second EARS event in April this year. We never intended to fly at Big EARS but had a few rockets to fly at the April event. At the event we only flew two of them. Mainly because of the good attendance and having to wait our turn. Eventually, time ran out and we left for home.
We managed to get to the October event. Very few people there. In contrast we managed to fly half a dozen times, it could have been more. The support we had was fantastic. I learnt a great deal, my grandson much more.
The lesson learned for me was that if you want an event to fly lots, pick one that is likely to be poorly attended. A very self interested comment I know, and "off the record" of course.
Back to "on the record" I do believe that attracting young people to hobby is key, also publicising the hobby both locally and nationally.
Schools, colleges, local demonstrations, may provide such interest. It has to be credible and sustainable however. There's no point in inspiring interest if it can't be maintained.
UK Industry must be supportive. Forgive my bluntness but I don't think it can supply the current demand let alone an increase in new member demand. Would they be prepared to pay for a planned campaign of "advertorials" in support of UKRA articles in relevant publications? By relevant I mean BMFA News and other UK flying publications that I see on supermarket shelves (to begin with). Product discount deals for UKRA and selected club members?
Publicise and appeal to parents anxious to educate and take their children away from Facebook.
Introduce challenge by way of competition and as you say, do it at a national event with national recognition. Make competitions achievable for all levels of rocketry experience.
Aerospace industry involvement, they are currently crying out for a good apprenticeship business cases. They have to backed by credibility and again, sustainability.
Change the UKRA qualification and certification rules to allow more beginners to be involved with qualified mentors.
Most importantly, get us overworked enthusiasts involved (at this point, don't ask me how, I don't know). But clearly we can't expect a few volunteers from UKRA and the clubs to do it all. To become involved however, we do need clear, informed and budgeted direction. That would be the part to play for those that control the hobby.
I recognise what you say about time and professional commitment, I am a "slave" to it as much as anyone else. Maybe however we could all contribute in numbers, in a very small way to something that could grow in a very large way. From a minor hobby into a sport?
A couple of final questions to UKRA and the clubs. What is the UKRA and club national membership number and do they publish annual accounts? A good starting point to indicate what is and what isn't possible.
I'm up for playing a small part in change. But I'd like to know that there is value and support from authorities, enthusiasts and industry to what we are "buying into".
All the best SO.