The amount of complexity that could come with the Architect and Align phase could be staggering if all aspects were drilled down to low levels concurrently. The secret is to focus on the process architecture and use it to determine major impacts on the other aspects of change. Then the remaining phases can take over and build the detail as part of each initiative that has been prioritized by the alignment.
The next phase, the Vision phase, deals with setting up each process project in terms of its expectations, objectives, scope, plan, and business case. It will leverage work done and will reuse the reports and results from both the Business Context and Architect and Align phases.