This October marks 40th years since The History of Middle-earth book series began with The Book of Lost Tales: Part 1.
To celebrate, I have an idea for the publisher, HarperCollins, to do. Please note that the following is speculation only. HarperCollins, if you're reading, please do ahead with these if it's in the cards to begin with.
Each of the 13 (12 + the Index) books will get published as 13 individual hardbacks. These hardbacks would feature the same imagery by John Howe (some of which appears in this post) that adorns the current paperback counterparts. The dustjacket would be arranged and designed in such a manner to match the latest Tolkien hardbacks, such as The Fall of Numenor and The Nature of Middle-earth. Much like The Nature of Middle-earth, there won't be any artwork inside - the only imagery would be what's currently available inside the 12 books.
Each of these hardbacks would be available on their own, and there would be 3 boxed sets (of the same editions). These boxed sets would mirror the 3-part omnibus editions, and would be as follows:
BOXED SET I:
The Book of Lost Tales: Part 1
The Book of Lost Tales: Part 2
The Lays of Beleriand
The Shaping of Middle-earth
The Lost Road and Other Writings
BOXED SET II: