Just a couple really quick things... I'm probably way in over my head, and certainly have no educational/professional credentials to critique your work, but maybe something here will help.
First, I'm sure you're already all over this, but would it maybe be beneficial to raise certain examples of where humanitarian intervention, if such a term exists, should have been applied but were not during modern history? For example, the Rwandan situation has not been brought up yet, and it would seem to me like that would be a prime target of examination. What was the difference between Rwanda and Kosovo? What makes one worthy of intervention, while the other struggles for media attention and goes (relatively) unnoticed.
Second, what role does public opinion play in whether or not a country decides to intervene? Does media outcry affect a foreign policy, and would a government intervene in a human rights situation just to placate its citizens?
Finally, billgiddens* made interesting points about a selfless act. However, I would say while selfless acts exist on a personal level and can certainly happen in individual situations, what government would possibly formulate a selfless policy? Doesn't the very nature of a country's existence mean any decision should be made for the betterment of the country itself, either short or long term? If that is the case, there cannot be truly selfless policy formulation, for if it did exist, then wouldn't that harm the country? If the country benefitted at all, then it wouldn't be selfless either.
Hope something in here helps... good luck while I'm not too well versed I do find the subject pretty fascinating.
*EDIT