Do any licenses exist that might serve the purposes below? If not, what licenses might be similarly useful?
Initial license goals
"Drive updates back to the source." My team seeks Creative-Commons-like (...we think?) license with addition(s) to either 1) strongly request or 2) require that modifications of original work be contributed back to the source content (eg: a github.com repo in the form of a pull request).
Enforceability. We do not expect these terms to enable any meaningful form enforceability for those who do not honor the license or "request." Rather, we simply seek to clearly state out intent and preference to more-honorable users and contributors.
Non-sensitive content. We have no concern for loss of rogue-editors source-documentation updates that are not contributed back other than the opportunity cost of the stakeholder community not benefiting from those updates. eg: there's no sensitive content or trade secrets contained in the content. We're simply (mostly) attempting to repackage general community knowledge in a more-efficient presentation.
Main application. For the initial, targeted project we want to create and foster creation of freely-accessible and freely-distributable documentation--and probably not software. At risk of being a bit repetitive: in the license for said application we want to encourage and/or motivate editors to contribute changes back to source repo so that all community stakeholders can benefit over time.
Our team's background
We are not (yet) well-studied in open-source licenses or the depths of difficult legal contracts. As such, please do not let our above "Creative-Commons-like" suggestion deter you from suggesting a significantly-different (from Creative-Commons-like) path.