Snowbird Games, creators of Mount and Blade: With Fire and Sword, have announced their upcoming project, Caribbean , that brings many of the mechanics of M&B to a 16th-century swashbuckling setting. The Mount and Blade series is definitely in that "high investment, high reward" category that only really works on the PC (with the likes of EVE, Dwarf Fortress, and Day Z). It's also about as close as you can get to a full-blown Game of Thrones RTS.
If commanding hundreds of scallywags in real-time boarding missions interests you, read on.
Snowbird's announcement cites a trove of ambitious features, including:
The devs say you should be able to get your hands on the buccaneering goodness this September.