Map decisions, then teams
Before drawing a system diagram, list the decisions the organization makes repeatedly, who owns each one and what evidence it requires. The map exposes duplicated authority and orphaned decisions long before either becomes a defect in a workflow.
Every handoff is an interface
Where work passes between departments, the system will need a contract: a definition of what is passed, in what state and with what guarantees. Designing those contracts explicitly turns informal handoffs into observable, measurable steps.
Design for the organization you have
Architecture that assumes a reorganization is a plan waiting on someone else. Build for the current structure, keep component boundaries aligned to ownership, and the architecture will survive the reorganization when it comes.