Thank you. You have given me much to think about.
1) Monasticsm- yes, I guess it would make sense for the leader to make sure his monastics teach straight down the line dhamma from the suttas (yes, it would be a particularly 'middle of the road' interpretation). Also I see that there is no harm in letting lay people teach the same interpretation, especially where monastics are in short supply (or even concommitantly). There is the assumption that monastics are 'professionals' in the matter and lay people are part-timers, which may or may not be true of course. Also the Buddha instructed us to learn from those who have attained to a higher state than a lower state- there is more of a chance of this being a monastic (on average).
2) sticking to 'lineages' is a problem. I guess practitioners must be encouraged to learn how to differentiate true dhamma and true dhamma teachers. The Buddha simply said to follow practices which will reduce craving, aversion and delusion, whatever the source was. Those foundations will be helpful when the leader is no more and the dispensation is in free fall.
3) by 'dhamma continuum' I meant standardising what is taught. This will ensure the true dhamma is taught. People can check with centralised sources whether the interpretation of the local teacher (lay or monastic) is up to scratch and in line with the suttas. Within that framework, the instructors would be free to expand, elaborate, give personal opinions as they please. It is important for a dhamma teacher to be able to speak from the heart and their own experience. I guess if they are taught to evaluate meditation methods using basics of mental cultivation, they could even comment on meditation methods of other teachers, outside this framework.
4) Large gatherings are suspect. I agree. They appeal to the masses. The Buddha had the lay/monastic split to perhaps denote serious practice with the less serious. He did teach each group slightly different 'strengths' of dhamma. I guess the challenge for this leader would be to make monasticism more accessible - make it seem less of an exotic unattainable form of practice. Maybe shorter term, say 2 week, 'ordination' may be helpful in making monasticism less alien/foreign. There maybe other ways I haven't thought of..In ancient India it was common for the youngest in the family to leave home and seek nibbana, apparently. Why not make it accessible?
5) The Buddha said he was a kalyanamitta to everyone. He also encouraged seeking a teacher for whom you felt affection and a strong sense of moral shame/dread for. These qualities are crucial when difficult bits of the vipassana nanas are unfolding inside of practitioners. I think the 'pot-puri' approach to the dhamma is a modern invention (and not a bad one under the circumstances). I think it would be best to tap into the mass acceptance phenomenon to recreate this within an international audience. But it will still be difficult..