Really, the Sun Keep poses an interesting problem. I'd like to include it, but I have to guestimate where it would be on the non-Lavos ravaged world map. When Lavos appeared in 1999 in the original timeline, his attack effectively rearranged the planet, which caused the Sun Keep to rise. Without that geographic change, I'm not sure if it would rise, and if it did it's sort of question as to where it should go. I figure that Lavos was probably at the center of the rather drastic planetary changes that went on through the years (between 1000 AD and 1999 AD, there's actually a fairly large amout of continental drift, and of course, we can't forget the appearence and dissapearence of the Tyrano Layer in 600 AD).
That being said, I might add it in on the final map once I've studied and compared the current 2300 map with the CT one to figure out where it would most likely be located. I think I might put together a tectonic plate map based on the contiental drift through the years to see which direction the island might have come from. The sun keep was to the southwest of Zeal's main island, and I guess if we figure they all fell at the same rate, that would place the Sun Keep somewhere to the far south west of Medina, perhaps off the coast of Porre.
Of course, this rises the other question--there's a Sunstone in Guardia (though it's most likely in Porre's possession at present). So if there's also Sunstone in the Sun Keep... >__>
I wonder how they handled that question in Cross...