Seems the issues would be synchronization. I tried using the current trainer in a multi and it would 'appear' to work to me but the options that required money were not working nor were my 20k armies beating tiny city-states... instead retreating. It seems that without somehow being able to make the game sync your stats with everyone else's it wouldn't be possible to work. But if someone designed a trainer that could work for multi, that would be really cool.