This is is not currently in our near term development focus. It has been placed into moved to the longer term backlog.
Ideas may be graduated from the backlog as we get through the ones that are planned.Rob Melocha commented
We are currently is a possition where eBook access is not sufficient to satisfy demand and so are occasionally scanning a chapter even when an eBook is available to help alleviate this. If option of placing a digitisation requests when an eBook were completely supressed we wouldn't be able to do this. An overide within the reading lists would be useful (an extra step that had to be taken before the request could be placed) might help.