@Mat
Did you ever try Red sands mod ? There they added some new items, and made eng_items.txt (for all old items) and eng_newitem.txt for their new ones. But there is only 1 items.txt file, and all new are in it. There is no newitems.txt. I`m not sure, will it work if you split all original items from game in items.txt, and place all your new mod items in tommitems.txt (just example for file name).
Try it out, i think game search for cod lines in game files. maybe you can split all new mod items in 3-4 files, but also you`ll have to make eng_tommitems.txt file for every one of tommitems.txt files.
Try making 1 try, with split items.txt , and all first lvl tomes in tomm1items.txt and add eng_ file for those items, if it work you`re golden
If not, i`m out of ideas
