I read this on IMDB:
"During its long development process, 'Rambo' went through a number of story premises. One un-produced script featured Rambo living a quiet life with wife and child, until white supremacists kidnap his family. Another script found Rambo trying to stop a hostage situation at the United Nations, where he is working as a diplomat, when terrorists (including Rambo's adopted son) take hold of the UN headquarters in New York."
So there's hope storywise
But the second idea (hostage situation) seems more a job for Bruce Willis
Ya, I followed the development of RAMBO for awhile and remember all those potential plots. I think it was just a challenge of what sort of situation fits the Rambo character as he had been established, but also fits for drawing a 60 year old soldier back into action and I think what they finally went with was fitting. I was weary of a Rambo 4 when the family kidnapping story seemed close to what it would be, family just doesn't seem like Rambo, reclusive is definitely more his style.