So far it is in the idea phase only. I'd like to try and create as many unique locations as I can.
Here is a very rough idea using locations from the pirates of the caribbean movies:

One of the bases would be the aztec gold cave from Isla de Muerta, I'm thinking something like having the control point be on top of a pile of gold. While it's tempting to just reuse that for the other spawn too I think being more unique would be better. The other spawn I want to take inspiration from Shipwreck Cove, being some sort of wooden structure in the middle of a cove of water. I already had this idea for a scrapped ctf pirate map so that much is good.
Trying to make each area unique, but also flow with each other, is tough. The island coast and isla de muerta flow fairly well, but things like the swamp -> cannibal village, or cannibal -> village are tough. That in general is a hard one but it would certainly be unique. The cross section between island coast and cannibal village is going to easily be the most challenging to connect. I think the height issue of the cannibal village might make that a bad location as all connectors to it need to height compensate.
Right now I'm mostly interested in thinking of unique locations, so all the nitty gritty stuff can be done later. I'll try to make a very very rough mock of it in hammer in the next few days.
I am a busy person and mapping takes up a lot of time, so I don't expect this project to be done for possibly an order of months. But I figure it would be fun to post my progress and encourage others to make similar threads for their progress too. This will be a great personal challenge for me because to create it in the way I envision will require a lot of displacements, and a lot of good aesthetics, both of which I am poor at. It will be a learning experience either way.
