To be honest I think that Next Actions are one of the most important steps to accurately walk through in GTD. A project list is in effect not much more than a reference list to be used by you in your (weekly) review. In the review you decide if you need new Next Actions.
Therefore you could set it up as simply as using contexts to create you Next Actions with. Then use another context "Folders" or just set up a folder with all your Projects listed in there as seperate items/tasks.