A few tidbits that you may find interesting:
NORTHWOODS appears to be a code word to cover the Pentagon's contingency plan to invade Cuba, and covers a wide array of activities beyond the false flag stuff. It appears in documentation before the false-flag memo is ever requested and continues to be used well after that memo disappears into oblivion. The only common denominator in the various memos' subject matter is planning for the invasion of Cuba.
The "NORTHWOODS document" isn't a plan. It's a set of proposals "suitable for planning" that were to be discussed as possible courses of action. Calling it a plan is far too grandiose and generous. DoD was asked by Lansdale on 5 Mar 1962 to come up with the list of "suitable proposals," due exactly one week later. The resulting proposals range from vaguely defined to far fetched scenarios reminiscent of something dropped by a James Bond film.
The request for the false-flag proposals came from the Special Operations Group -- Caribbean, an interagency outfit that Lansdale ran and RFK oversaw. The minutes for that particular meeting still exist, IIRC. They seem to have been thinking more along the lines of faking a "Cuban" landing on the beaches of Guatemala or Honduras. It's not something that Lemnitzer pulled out from the bunghole on his own.
In 2017, an interesting document popped out from the Archives. It's a memo from someone in DoD who is explicitly responding to a request from the Attorney General for detailed information on the feasibility of creating a US-produced MiG jet fighter. Interestingly, this reflects one of the NORTHWOODS proposals. More interestingly, the memo was generated about a week after the set of false-flag proposals had been presented to McNamara. It's seems RFK was still interested in at least one of the proposals even after it had supposedly been killed.
The fact that something like this with all of these incredible idea/thoughts/proposals to kill people or let them die and blame Castro made its way to the White House is simply unbelievable. Yes, we know the Kennedys - RFK in particular - were pushing, pushing, pushing for the removal of the Cuban regime and they were responding to this but to let some of these ideas work their way up the chain-of-command, to actually be put on paper, is stunning. I'd like to think that Lemnitzer et al just threw their hands up and pushed this out to Landsdale. Or Lansdale took it in response to the pressure from the Kennedys. Where it was rejected out of hand. Maybe that's a defense, that they were winging it and weren't serious.
The source of the problem, as I understand it, is that the Kennedys wanted - demanded - that Castro be removed. The Pentagon responded that the only way to do so is with American force, that it couldn't be done internally and that none of these hit-and-run attacks would work. So they came up with these ideas to justify such an act. It clearly got away from them, they began to embrace ideas that were simply appalling. Such as: blame Castro if/when a
Gemini Mercury rocket launch explodes on the pad? Really? You're going to send this to the President?
As you said, these were ideas or proposals. I don't think there's any evidence they went further than that. And the idea that these were somehow a blueprint for the assassination of JFK - John Newman argues this for example; Morley promotes it (sort of; he's just, frankly, dishonest) as well - is groundless.