Sorry, i kept forgetting the books are letter, not Legal size. I'm casually work in copy/printing industry so i get confused sometimes about the size of the TROs.
Its too bad PoD so inflexible. I made my own combination of all the primitive XTRO for myself to read and used GBC comb together. It came reasonably fine.
I've been in many a copy/print shop alleged to be state of the art, but state of the art maybe in later 1990s or early 2000s.
Cost make a book cover and being glued must been main issue i suspect.
Either case do what guys need to do what you can do to put book out, but i can't say i will like it as much as Landscape oriented book. They fit better in my bookshelf anyways.
Now I'm imagining someone setting up a small PoD shop that only does books in Landscape format, with the short side as the spine. Everything is set to be flipped on the short edge, so you could even have a regular book printed by them, but it would be read top to bottom, where page 20 is above page 21 (instead of standard books where page 20 is to the left of page 21).
Though technically you could have the TROs displayed Landscape mode, and use the standard long-side print option. When you read it the spine is horizontal, the details about the Mech/ASF/vehicle/satellite/station/Jumpship/Warship/SupVee/Structure are on the top half (above the crease), and the pictures are below the crease. The layout is the same, you just have the spine horizontal instead of vertical. This would allow TROs to retain the landscape format, yet fit on a shelf like regular BT books and still have their spines easy to read.
The spine text would be set up similar to the footer on a page, but instead of using left/center/right formatting, it will use top/bottom formatting, so the stuff in the top (i.e. title) is printed at the top of the spine, and the stuff at the bottom (i.e. book number) is printed at the bottom. This way no matter if the book has a long or short spine, the data will be laid out the same (though someone will need to make sure the length is short enough to fit on a short side spine).
The key with either option is making a sturdy spine that can handle being opened and closed often, plus being left open, all without wearing out too quickly. If that isn't practical, then printing out the sheets and putting them in a binder notebook will be necessary.