Okay I think i might have found a work around but it involves a mod. If you already don't like that fine keep waiting. Otherwise, go to the steam workshop and look up: DarthMod: Shogun II SW v5.0 and subscribe to it, wait for it to download, and then start playing Shogun 2 , and then you can turn on the trainer at the main menu.
That being said its not the only mod that running and i haven't tested it with anyone else can I please get someone to test it out as well? Also to note I've only been playing it with fall of the samurai, and since god mode activates as soon as you turn on the trainer i don't turn it on in the interface.