Pretty simple, if you have Shipbuilding, the City-States you are suzerain of would generate Treasure Fleets for you, from their connected Treasure Resources. Would spice the economic legacy path up a bit. (Pun totally intended)
#Suggestion: City-States generate Treasure Fleets
rugged whale
young mauve
I think this is a nice simple addition to the exploration era - I would add perhaps a small influence cost as well (adding it to the menu of actions). A nice way to peacefully expand to distant lands and a good contrast to the military goal.