Please include individual Open Access articles that are published in subscription journals.
Many subscription journals include individual articles that are Open Access. These often carry a CC licence or can be Identified using the NISO standard: http://www.niso.org/workrooms/ali/
Please include them in the Open Access collection.
Eike Harden commented
In Göttingen (Germany) there has been an initiative to address some of the problems posed by hybrid OA, see e.g. https://subugoe.github.io/hybrid_oa_dashboard/about.html
Perhaps the techniques used there will prove helpful for finding a solution.