Looks like we could try to do this without changing HEAD development at all - if Alex starts with OpenID and Aggregator 2.x branches in contrib, then anyone who wants to could do the same for the other optional core modules. Then if it works we could look at better infrastructure around it.
No insults, but we don't really want to start wild forks of core modules with arbitrary maintainers and features in contrib. If we just do that, the quality of those forks won't differ from any other contrib module, and I would not see nor understand why those forks can't use a different module namespace (like any other module that thinks it can do better). Additionally, system module's updates would need to be properly split up into .install files of the respective modules or they'll run unintentionally (i.e. twice for straight back-ports of stuff in HEAD). sun