For symmetry, have you considered documenting the transition of a specification from a Working Group to a Community Group?
If this direction would be well specified (signals to look for, policy/CLA considerations, etc.), I believe it might in fact encourage incubation efforts to transition to standardization in a timely manner knowing the conditions under which there's a path back to incubation within the W3C community.
I think this would help establish a CG <-> WG continuum and as such encourage broader participation in Working Groups when combined with the proposed Support for continued participation in a Working Group by CG contributors.
This would be especially helpful for Working Groups that have sister Community Groups that act as their domain-specific incubators (example) with good overlap in participation.