I did mention this idea at our F2F meeting, but I will suggest it here again.
I think that the field of open access textbooks can become a research field and that if it does, conferences and papers that address ideas and updates, both to the texts and to the support materials, will encourage faculty to enable the currency of the works.
In addition, moving the texts to a state where Data Mining can be applied will aid with the future design of the works.
Best,
Dianne