If I interpret your comments correctly, the point you are making is that one should look at (in business terminology) through-life costs and 'can I afford these' before embarking on a project. This leads me to think that the Natural Planning Model for projects should allow one to recognise that it may be best not to do the project at all! Suppose I own a bicycle and am thinking of buying a car, I create a project "Buy a car". But maybe, when I look at all the costs and responsibilities involved in car ownership, I decide that making do with the bike is the best option for me. Or maybe using the bike and hiring a car when I really need it. The need is transportation and owning a car is just one means. This kind of "requirement scrutiny" is not part of the Natural Planning Model but I think it often needs to be done at some stage. To take a non-project example, if I have a Next Action "Call Jeff to ask if he would lend me his car", perhaps I should have first considered some options - call round to see Jeff to discuss this, send Jeff an email about it, meet Jeff down the pub and buy him some drinks and only then, when he is in a relaxed mood, raise the subject!

So, the "unconscious reasoning" then becomes explicit.
Looking at this again, something has occurred to me. David Allen often has what he calls "R&D" (research and development) projects e.g. an example from the book "R&D joint-venture video project". Maybe one should liberally use R&D projects to both research the topic and to evaluate the best means to achieve the ends.