vague notion I hope other will flesh out

Don't forget the National Space Society (formerly L5 society
and NSI) which has about 40,000 members - I believe second
only to the planetary society. NSS may have difficulty internally
agreeing on an agenda, but they did put together a roadmap
recently: http://www.nss.org/community/roadmap/index.html
which goes beyond cheap access to space to provide a common
(if perhaps obvious) agenda with milestones and barriers to
their development. The different groups may still disagree
on which milestones should be reached for first, but the
existence of an agreed set of milestones is at least a first
step to a common agenda...