Hi George,
At times I wonder if Software Architecture isn’t overrated. What it comes really down to is exactly those decisions. In the projects that I have been involved in we always had two leaders: a) the project manager and b) the architect. The project manager is the financial/organizational decision maker. The architect is the technical decision maker.

I usually try avoid detailed models, but try to lay out clear structures, metrics and the fundamental design/principles. Then we start development. What seems to be important about architecture is that the right areas/decision-making points are addressed. Projects can may fail because of a wrong architectural decision, but they are more likely to fail due to a decision that has been overlooked and not been made at all. This is where I see the importance of architecture work. Identifying all areas that could be problematic early one. Just as you talk about in your risk-driven model.

Regards,
Michael