Preserving the direction isn't important (yet). id1 will always be the one to have 'created' the trade, so if I check the nation's trade->id1 against user.id I can figure out the direction.
Although after switching the brackets to curley brackets (how I missed this I dont know haha) I get this instead:
"Can't locate object method "nation" via package "DBIx::Class::ResultS
'nation' is defined via a belongs_to in the Trades schema. This makes me think that you are correct about not being able to use belongs_to for more than one owner.