One of the (for me) shortcomings of the online plans was always the crappy repro of the photographs. I agree that having a good photo of the finished engine is a big help in understanding what goes where. This is especially important when building most of Elmer's engines for the first time. After a few, you see how Elmer used similar parts and relationships.
As far as re-publishing the book. I can't tell you how many times I've read that the reason is the cost of publishing for a relatively small market. That is a load of bull. Sure, years ago, a book could only be printed by setting type, making halftone negatives and plates, setting up a press run, sending the printed pages to a bindery, etc., etc.
Print-on-demand (POD), hardly a new technology, only requires that the copyright holder or publisher send (electronically) a PDF of the book to any one of hundreds of POD companies, set a price and sit back.
When a book is ordered from the POD website, a big machine prints, cuts, collates, binds and spits out a book. Doesn't cost any more to print one or a thousand. The copyright holder gets a check (usually quarterly) in the mail while sipping his beverage of choice.
If anyone knows the guy who owns the copyright, I'd be more than happy to get the files in a proper PDF format, do correct scans of the photographs ( if he has them) and set the whole thing up at a POD company. No charge. Just for fun.