Hey Max,

There's a class of metrics that might be relevant to your purposes. I refer to them as "content persistence" metrics and wrote up some docs about how they work including an example. See https://meta.wikimedia.org/wiki/Research:Content_persistence.

I gathered a list of papers below to provide a starting point. I've included links to open access versions where I could. These metrics are a little bit painful to compute due to the computational complexity of diffs, but I have some hardware to throw at the problem and another project that's bringing me in this direction, so I'd be interested in collaborating.

Priedhorsky, Reid, et al. "Creating, destroying, and restoring value in Wikipedia." Proceedings of the 2007 international ACM conference on Supporting group work. ACM, 2007. http://reidster.net/pubs/group282-priedhorsky.pdf:

Describes "Persistent word views" which is a measure of value added per editor. (IMO, value actualized)

B. Thomas Adler, Krishnendu Chatterjee, Luca de Alfaro, Marco Faella, Ian Pye, and Vishwanath Raman. 2008. Assigning trust to Wikipedia content. In Proceedings of the 4th International Symposium on Wikis (WikiSym '08). ACM, New York, NY, USA, , Article 26 , 12 pages. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.141.2047&rep=rep1&type=pdf

Describes a complex strategy for assigning trustworthiness to content based on implicit review. See http://wikitrust.soe.ucsc.edu/

Halfaker, A., Kittur, A., Kraut, R., & Riedl, J. (2009, October). A jury of your peers: quality, experience and ownership in Wikipedia. In Proceedings of the 5th International Symposium on Wikis and Open Collaboration (p. 15). ACM. http://www-users.cs.umn.edu/~halfak/publications/A_Jury_of_Your_Peers/halfaker09jury-personal.pdf

Describes the use of "Persistent word revisions per word" as a measure of article contribution quality.

Halfaker, A., Kittur, A., & Riedl, J. (2011, October). Don't bite the newbies: how reverts affect the quantity and quality of Wikipedia work. In Proceedings of the 7th International Symposium on Wikis and Open Collaboration (pp. 163-172). ACM. http://www-users.cs.umn.edu/~halfak/publications/Don't_Bite_the_Newbies/halfaker11bite-personal.pdf

Describes the use of raw "Persistent work revisions" as a measure of editor productivity
Looking back on the study, I think I'd rather use log(# of revisions a word persists) * words.

-Aaron