Our PS team is actually using Maven in a similar fashion and I think we're slowly moving towards something like that for plugins, I'll push a couple of our Maven guys to respond here with their thoughts.
Thanks for your question.
Our PS group has just started using Maven internally for customer projects. Currently we only have an internal Maven repository, where we post each new Clearspace version, which we incorporate as a customer project dependency. Upgrades are much simpler that way. We have new project and plugin archetypes as well. Our plan is to create a public repository with SSO to Salesforce.com, where partners and customers could access these maven artifacts using their login information in Salesforce. Timing of this will depend a bit on the partner demand for it, so please clamor for it. :)
Those are some interesting ideas for sub-components. We currently don't have the project broken out into sub-components, as that would be best handled by the product team. Maybe you could elaborate on the reasons for breaking those out.
In the near feature we will be exposing a maven repository at jivesoftware.com with jive libraries and dependency info. We will also have an archetype for creating plugins.
For deployment you will still want to use the library set from the war file. We occasionally make bug fixes to third party jars that won't be posted. Also we won't be posting jars for proprietary libraries such as coherence.
Seeing scattered comments and references that this might actually have already been done. Could you provide the URLs and/or a link to the documentation for linking up to the Jivesofware maven repo...if it is available? I'll continue to look for the REPO configuration information elsewhere =)