Your friend might be getting good results from his V750 but this is hardly a viable, high volume commercial production solution and while you can stitch 2 A3 scans it is a laborious and a slow process so if your original is larger than A3, your options are limited to either a camera which is fast and consistent or an e.g. Zeutschel type scanner which is very, very expensive and slow.
Never said our scanner modification was for industrial quantities and all his books are smaller than A3.
It's just a nifty way of delicately getting into the gutter of the book (deep area along the spine between pages).
He also wanted this option because he preferred to do the digitizing himself rather to take the books somewhere.
There are still several large format scanner manufactures. They use plotter type machines that either drag poster sized originals through them
sort of the way large format roll printers work. Some also have a large tray that can support more delicate originals.
However scanning is always "lighting limited". An oil painting for example has relief to it as well as the image depicted.
Using a camera lets one light the original artwork in different ways.
I recently photographed some modern art that had quite a bit of relief on it... up to about 1.4 of an inch. They looked the best
when light form one side only, but with the light source quite far away so as to keep the fall off from one side to
the other as little as possible.