I think you have a handle on it. You may need to experiment a bit to find a way of doing it that makes you happy (or, at least, less irritated). For example, if you're sharing your tree online via Ancestry.com, putting a narrative into citation notes will be too hidden for most users to find, if it even displays those (I don't recall). I do know that if you use source notes, then someone visiting your tree would have to follow two links to get there, first one to see the citation, next to see the source.
If you're using 2014 then you should be able to just copy and paste the custom fact from one person to another, and then you don't need to worry about forgetting to source one. You can also filter your index to limit your list to people you'll want to create this custom fact for. That's probably how I'd do it anyway.