GTD reversed approach

Many people complain that GTD does not provide too much detail on the goals and values.
There are few articles listing disadvantages of GTD in this matter and they are right in certain way. But I think we should look at this differently.
GTD is a very close to ground system. The main focus goes on actions and projects. On organizing things you have to do. As much as important value and mission statement is this is beyond scope of GTD. The value of GTD comes from helping organizing what to do and how to do it - think, plan, do. I guess once you figure out your values, mission statement you can perfectly apply this into GTD. You don't have to start from the bottom. Although main point of David Allen's methodology is bottom up system you can work top down as well.

Use altitude levels as guiding principles.
50k - values, mission statement
40k - goals 3-5 years
30k - goals 1-2 years
20k - areas of responsibility
10k - projects

The main assumption is that you need to ignore what is going now in you life and focus on the top level first and then go down. As listed above start with assessing your values and then move downwards.

I think this approach will work perfectly as it allow you to establish the direction and bones of GTD will help maintain progress.