You actually only need a grain exchange & 20% judaism.
Copied from DLV5.2 EDB...
Code:
corn_exchange city requires factions { northern_european, middle_eastern, eastern_european, greek, southern_european, }
{
capability
{
agent merchant 0 requires factions { aztecs, } and region_religion judaism 20 and event_counter introduction_aztecs 1
agent merchant 0 requires factions { byzantium, } and region_religion judaism 20 and event_counter introduction_byzantium 1
agent merchant 0 requires factions { denmark, } and region_religion judaism 20 and event_counter introduction_denmark 1
agent merchant 0 requires factions { egypt, } and region_religion judaism 20 and event_counter introduction_egypt 1
agent merchant 0 requires factions { england, } and region_religion judaism 20 and event_counter introduction_england 1
agent merchant 0 requires factions { france, } and region_religion judaism 20 and event_counter introduction_france 1
agent merchant 0 requires factions { hre, } and region_religion judaism 20 and event_counter introduction_hre 1