Mayby no short time solution, but...
what about instead of splitting the Region of the carribean sea, adding a new region like Europe with North and balitc sea and mayby even the Mediterranean Sea.
It would need work to build the map, which depends on the Game Engine the dev's use. If it's managable have the dev's to decide. So an Idea for the long run.
It would have the benefit, that you don't have to worry about what happens on the other PvP Server and allows you to syncronise Players on both Servers.
You could Keep your Money and XP, even your goods on both Servers without any harm, but would need to ship things from one Server to the other.
To get from one Region to the other there would need to be Transferpoints at the edge of each Region. They could act like those Portals, you spoke of, used in EVE (sorry, never played it).
Another benefit would be the bigger variety in Nations.
Depending on the map-size sweden and Denmark would gain some more ports.
You could intreduce Russia, prussia and even some smaller German states.
If you can cover the Mediterranean you can even add Portugal, Venice, the Ottoman Empire, Austria and others.
Mayby even introduce Mediterranean shiptypes.
The bigges benefit would be avoiding to split the Playerbase and force guilds to choose a Server.
It's just an Idea and the Dev's have to see if it is a possible solution.