Based on sources (1) (2) (3) I am now confident enough to say that the South Pacific was not created in April 2003, as we previously thought. The NationStates ChangeLog mentions the creation of additional feeders on 29 April 2003, but also says that those changes were in previous months. The last entry before that was on 10 December 2002. Based on that date, and the earliest source that mentions the South Pacific, I would say that our region was created at some point between 10 December 2002 and 16 January 2003.

Though sources are probably scarce at this point, it really would help if we could all do some research on the creation and origins of the region, to know when is the first mention of its existence, and maybe what happened during those first months. Two things we already know from that pre-KM time:

• Bong Load was the first known Delegate, as mentioned in this, this and this posts, and confirmed to me by him through telegram.
  
• Katland might have been the second Delegate, as claimed in this post, though further confirmation would be appreciated.
  

There might not have been a functional government during this time, since it is widely believed that Killer Monkeys and Goddessness established the Coalition in the Original Forum. Still, I really hope there are some extant records or accounts of this time, that we can salvage and use for the Historical Project.

Thanks to TAC for giving me the original source about these two previously unknown Delegates.