OK how to make piracy work in D&D. I'll post some ideas from an okdc2E game. We used gunpowder weapons from combat and tactics.
I cant remember all the details its been 27 years.
1. Big bads. Elven imperialism. Mix Rome with Driw and the British Empire.
2. Domain rules. In 5E this is bastions. PCs had a hone base "Port Royal". They used the loot to build a shipyard. This was to service their own ship then small fleet.
3. Population. Rescued slaves. Elves were slaves.
4. Turns out the Elves had factions. Only tbe worst ruling house were tge demonic loving ones. The second house was elven Sparta and formed the bulk of the Empires military.
5. Elf emperor was dead killed by a Hunan paladin. His sword was missing.
6. Buried treasure.
7. Based out of not Africa. This gave them access to ivory and a place to grow crops for rescued NPCs in their Freeport.
8. Exploding gunpowder barrels with bolts inside them duplicate fireball well enough. Force, fire, piercing damage pick your poison. Gunpiwderci would probably make fire danage. Smoke or rune powder force.
9. Vampire spawn with guns. In 5.5 turns theyre roughly on par with a level 5 sorecererous burst spell ut piercing damage. Exploding dice mechanic.
10. A pet elephant became a major NPC. Trained for battle, enchanted boarding, stoneskun spell. Towards the end they wanted to build a giant trebuchet and have Ninja Clive parachute onto enemy ships via feather fall.
11. Custom magical cannonball and spells. Think fireball AoE crossed with old school disintegrate spell.
12. Lost cities of gold. 4 or 6 legendary locations scatter them around.
Other general advice. Focus exploration more. Lost islands, South Sea vibes. Isle of Dread, Isle of the Ape type vibes. Lost treasure, a famous sword to find, ships a vehicle to get from A to B.
You need an enemy if youre not doing an evil game. I used a British Empire stand in. An awakened demonic orange dire ape following Demogorgan could work. Undead, aberrations, demonic or infernal foes works.
Steal NPCs from favorite pirate shows and game. Have a list of 8-10 captains tgat are famous. They're mini bosses. Cervantes from the Soul Calibur games sure.
Factions. Different nations, houses, merchant Guilds etc. I like 4. They're the not Dutch, British, French, Spanish. Replace with D&D equivalents. Keep the mockery to suitable levels (this basically means open season on the not British not French let's be honest).
Magitech. Can exist. Dwarves have monitors, Gnomes cave transforming submarines. Lighthearted tone.
Suitable research options includes Sid Meiers pirates and Assassin Creed Black Flag elements. The Isu are basically your not Netheril equivalents. Atlantis as well.