Mike's "Institutional Member" solution works for me.
Ultimately, we have to get those organizations and people involved for the scientific community to really believe that this is serious.
3.)
I hear the arguments against "2 full-time equivalent resources" to join the steering committee very well. That would be an enormous cost at ORNL and other US government organizations, even if you count interns and post-graduate researchers. 
However, I think it is important that members of the steering committee very obviously have skin in the game. I suggest that we replace that wording with "sustained year-over-year development from two or more persons" where development is purposely ambiguous to include code, content or any other activity that advances the goals of the working group. It rewards regular activity instead of money (which is what people see when they read FTE) and avoids the dreaded "FTE" acronym.
The steering committee would be expected to govern itself accordingly with respect to committee members who fail to meet this requirement.
Y-O-Y activity is impossible to gauge when the group starts, granted, but over time it will be very clear. I would suggest that the steering committee could be bootstrapped by nominations and a simple vote for the first year and the normal process could take over after that.
jm2c,
Jay