I don't know how many times I have encountered players on my crew that want to sabotage the ship or throw off hard earned loot into the sea. Don't get me wrong, the current system of having a brig is great and adds a passive-aggressive approach, so either a bad player can leave or they can make a plea and be allowed to join the crew again. However, when you have players joining your crew and intentionally taking skulls, chests, and other hard-earned loot and throwing it into the ocean, or crashing your ship into rocks... that's where the brig system fails. A kick system would be extremely beneficial to counter players that want to ruin the gameplay for others.
Also, what about those pesky players that you put in the brig and they don't leave and a friend wants to join? Or you're doing a skeleton fortress or voyages and that person in the brig doesn't leave and just bandwagons for loot? That needs to be addressed.