I’d personally be careful deploying SPS as a doc  management solution. (Doc Management is not what SPS does best nor do MS market the product as a document management solution like they did with SPS 2001)

You’ll need to investigate shared services to construct your architecture design

For a moment, skipping over the term "document management", SharePoint Portal Server 2003 server farm  architecture addresses WRoyce's requirements:

- 60K users
- 30+ locations  worldwide
- 20 datacenters
- high availability, no single  point-of-failure server farm architecture
- ability for each datacenter to store locally produced documents  with access  to organization's documents world-wide
- enterprise-wide search
- federation of central portal, division, group, team and personal sites using SharePoint Portal Server 2003 Shared Services (although there are caveats about using Shared Services over WANs)

Ask your Microsoft rep for a copy of 2 new customer-ready MS IT Showcase white papers:
"Microsoft Web enterprise  Portal"
"Deploying SharePoint Portal Server 2003 Shared Services at Microsoft"

Each white paper is about 32 pages long. These whitepapers are in the process of being published to Microsoft.com and will be available on the MS IT Showcase site: http://www.microsoft.com/technet/itshowcase.

Back to SharePoint 2003's document collaboration features:

1. Document checkout/checkin is supported (locking).
2. Version numbering is supported limited to major version numbers: 1.0, 2.0, 3.0, etc. Minor version numbers aren't supported.
3. Single-step "moderator" approval is supported. No serial, parallel or built-in customizable approval routing.

These features are baked into Windows SharePoint Services and available in SharePoint Portal Server 2003.

SPS2003 is not a DM solution. It is a Document Collaboration solution.