I like GI's suggestions, even though I do not know of the RP's that people have spoke about. For Hammerstar's list 3/6 seem the best for, somehow squeezing in a timeline there for their exploration, of which GI spoke.
What I have been playing around with on paper are two main continents that span the north, but don't surround the current landmasses, such as the Pacific does in real life. They would be long and thin, having around 30 large plots each. The ocean that wraps around would contain a few subcontinents/large islands.
The problem is, as Hammerstar brought up, is that they are too large too miss. Even if we fit them in the storyline, somethings will not add up right. Maybe our countries share a similar belief that their world is the only part of it and that going past it would be reckless. That could work historically, but now it is just stupid.

To sum up, I am in full support of completing the map, and would love to help, as I love cartography and making maps (same thing, who cares), and adding new continents could be tricky at first, but once the kinks are worked out, I think that it would be beneficial to the storyline of Pacifica.