Copying my bullets from the other thread.
1) Make this an extra-game group, one that doesn't use, or need, the in-game alliance system. That way, even "enemies" will be able to attend and share information.
2) Go with the representative idea; each group sends one or two people to serve as the liaison to the group. I'm imagining this as more of an information-distributing group than a decision-making body, so we don't have to worry about proper representation for group size, but if any kind of decision does have to be made it can be a straight up/down vote.
3) I'm a historian and a teacher, and an admirer of Thomas Jefferson. If you need someone to help lay out any kind of founding document... yo.
4) Name it something that sounds a) neutral or open access and b) awesome. "Conclave." "The Grey Parliament." "The Mercenary Court." "The Congress of Shadows." I personally like Conclave, because it resembles CONCORD, which is a known extra-group entity, and because one-word names are the easiest to make recognizable and definitive.
5) Require nothing from the groups which join it but the information they're willing to share - EVE corps which have shafted them, fits and loadouts that have worked or haven't, as much tactical advise as they're willing to share, etc. No calls for mutual defense or support - if need be, people can work that out themselves; what you're giving them is a place to do that.
6) Base this out of a simple website out of the game, and maybe even a location in-game; have the primary function of the website be to allow posting of information and the keeping of member lists.
7) Only have a few officers of this group, with simple duties, but give them badass names. For instance, the Archivist is responsible for sorting and uploading the information that groups provide. The Warden will keep member and representative rolls. The Prior will be in charge of appointing people to those various positions.
8) Any position, including the prior, should be subject to removal in the event of a vote of No Confidence with 60% of the representatives.