Hi Ben,
I think you've misinterpreted what I meant.
What I meant is that assuming, for example that a decision is made in your step 4 above that plone is going to be used, unless an implementation team steps forward with plone expertise, then the decision is fairly meaningless. Especially considering the resource constraints.
"Fifth we get someone to do implement the solution that's been decided upon. " sounds nice and simple, but doesn't tend to be how technical projects pan out. In my experience talented coders are more like artists and poets than people can simply say "implement this" to.
Also, while steps 1-3 are very important and very much need to be done (as people have mentioned elsewhere, people in Transition Network need to feel some ownership over the process) I have seen so many groups go through this process that I'd be very surprised if 2 of the recommendations are not drupal and plone. Indeed, I'd be mildly concerned if they weren't (because so many great minds have done this already and ended up with that conclusion). The requirements discussed so far are far from unique (indeed, they are fairly ubiquitous desires/wants).
Perhaps it would help if I were to write up a comparison of drupal and plone and their pros/cons? (based on the many existing ones out there, but bringing them up to date and adding my own perspective)