Is it possible to update a trainer just by having the Trainer.xex and Trainer_Loader.xex say the trainer was for a TU3 and the game has had a new TU so its not on TU4 and some of the offsets have changed
you could...but you need 100% source code... Info if any of the Poke Offsets Changed Or deleted, the title update Offset, Along with the game id *normally game ID's never change*
As Beastly says, you would need the original source code from the original dev who made that specific trainer to be able to update a game trainer and make sure the media ID (MID) is the same as the game that it was programmed for.