I know this comes up from time to time on Logos Forums, so I finally did something about it. One of the problems in the past is that the publisher, Banner of Truth, did not have reasonable text (i.e. docx) files for these volumes. So I went to work with their permission and developed edited and proofed docx files for each of the first 8 volumes of the set. I have not yet completed the remaining volumes. Of course, I have used these to make personal books for my own library, but I have talked to Banner of Truth about making these available on Logos.
My suggestion is that if Logos will approach Banner of Truth on this, I think that something could be worked out now. I have coordinated my work with John Rawlinson, General Manager at Banner of Truth Trust.