This is the first indication that something is rotten here. In my experience, it's virtually impossible to keep your own personal GTD project files in some big corporate filing system. So I'd strongly recommend instead starting with a step like starting a project in your own system, and adding 'start project in company's system' as an action.Let's consider an example where I have to write a report for a client. First, I start a project in my company's filing and accounting systems.
You're close here, but I think the emphasis has to be on writing stuff down, not thinking stuff up. Yes, you'll need to think stuff up too, but really the important GTD part of the activity is writing stuff down. "The next physical, visible action" sort of thing.Then I start thinking through the possible next actions.
I wouldn't get too hung up on how complete or NPM-compliant your planning is. No plan is complete. As others have mentioned, this sort of thing goes into the Project Support folder, which personally I often fold into the Project folder. Which you'll need anyway -- you need somewhere for the results of actions like "collect water use data" to persist.What do I do with the 7 possible next actions that didn't make my next action list? They don't represent a complete plan for the project according to the Natural Planning Method.
Thanks again for the great question, and I hope this helps.