I would like to propose Caelum Liutas as a Shichibukai.
What does he do?Liutas Liutas is an engineer and part of the Sky Tribe race, a great mind that harnesses dial in applications of all kinds, from everyday objects to advanced weapons and armor. He himself is an avid fighter with a tough, raw physique, a sign of a good portion of his life spent in beating and handling big scrap metal. A good general asset to his island thanks to the power of the pad fruit, with which he helped move large materials around the island or reach various places himself in a hurry to offer his services. Always on the front lines if any evil characters tried to harm the island and its inhabitants. Many years spent in this way greatly evolved his plans, especially in the field of weapons. The leader of the island, first amicably and then showing his true intentions, wanted to take advantage of his creations to make the entire population ready for wars to be declared. Since this was an idea that went against Liutas' mindset, he decided to leave the island and go down into the sea with a clear goal, to disintegrate with his force and weapons all particularly evil pirates, especially those who attacked innocent islands just to plunder.
This lifestyle led him both to help various villages with his inventions not dedicated to warfare, any kind of mechanism that might have helped some people, and to make a name for himself against various pirates all along the paradise and even in an early slice of the New World.
He does not seek money or riches; his goal is to make enough in the world until he can retire to a large island that he has been in charge of for a few years already by becoming both its protector and its mayor, this island is in the first part of new world and it's called Aetherius, it's a bit smaller than dressrosa but way more peaceful (page coming in the next days)
Knowing that the only certain way he could deal with pirates of particularly high evil was to side with the marines, Liutas in 1616-1617 offered his technology for a just cause. Funding from the world government would have made possible large-scale creations of his designs, being able to offer a remarkable power up to regular naval weapons. But that was not the only advantage; his strength and especially his hands were the key to fighting evil. With his power he began to wipe out the bad guys in a fight/victory/capture cycle, but in his case the capture had the unbelievable.
The great example of this cycle occurs in the war of empires. Throwing himself into the great struggle he managed to overwhelm like a beast large numbers of pirates, between the meat of the slaughter and a few pirates of higher rank among the yonko ranks, leaving an extraordinary clean sweep as he passed. How is that, you may ask? Every defeated pirate was sent straight to impel down thanks to the power of the pad pad fruit, this management of the war gave it the nickname "Purgatory Hand."
