After some messing around with Puyo Tools, HxD and Shadow Dragon modules, here's an unfinished Class Editor for FE 12! Use it on FE12Data.bin after decompiling and decompressing your ROM.
FE12 Class Editor.zip
By editing Blazer's module, I've made an Item Editor Module for Fire Emblem 12. Here you go! Use it on FE12Data.bin after decompiling and decompressing your ROM.
FE12 Item Editor.zip