Interesting. How many MB is the file?

I've noticed current Kindles and Kobos seem to easily handle very large files, once they're indexed. For example, I have a study Bible that's huge, in the range of 50MB, and both the Kindle and the Kobo open it easily, in a few seconds. Some of the open source apps like KOReader struggle with those huge files that have thousands of links and paragraphs in them--it'll literally take like 10 minutes to open a book. :-)

The OED of course, would be an even far larger file. You could wrap it all in a single epub container, and split internally into many indexed files. No idea how performant it would be with something that huge. Obviously upload/download would be a pain.