I know stuff about modding Warband because I had Warband and Mount and Blade for about 3 years, and I am very active on the Taleworlds forums, you can gather a lot of info about how the game works.
Now there is this mod, Prophesies of Pendor, where they specificy how people should NOT add new item to the mod, since its very close to the item limit and adding any more may results in crashes, I took a look at the cRPG item file, there is a fucking ton of items, considering that for 1 item you need to create 6-7 version for the heirlooms and broken version, you can see how quickly that can fill up an item list.