After a cursory search of the forums it seems to me that we have had many threads about changes being made to the League of Nations, and whether or not they would have helped. But it seems to me, that no one change could have made the League function, it would, instead, require a variety of changes to its basic structure, in order to accomplish what it set out to do.
As I understand it, a reasonable compromise would have to include.
Not a standing army, but some sort of military capability, be it recommendations or what have you (although it would need to be on some sort of regional basis, to appease the American congress who were afraid that giving the League military capability would lead to violations of the Monroe Doctrine)
and,
An executive council with actual decision making capability
What else do you guys think (that would have been plausibly accepted) could be added to an ideal League of Nations?