Anyway, back to the mapping portion of the topic.
Multiple maps could be used as stated earlier, but instead of using teleporters around the edges of the map, you could just define a region with 4 rect3D's that represent lines around the perimeter of the map and then handle the region's OnEnter, determine their direction of travel and offset their new location appropriately.
To avoid a player seeing the edge of the map (the 'void' / blackness), you can make the theoretical width of the region's lines say, 50 to 100 tiles and design the maps with an overlap of double that amount in mind.
Rather than thinking about it like they're adjacent cells in a grid or table, think of them as pieces of a blanket that are sewn together, where you must leave some room for the stitching (which tends to be hidden when complete)
In a sense, the way boats wrap-around the map when they meet the edge uses a similar concept - the map wrap bounds are defined a ways away from the physical map edges, to give the illusion of continuous sailing.