Hm... Kusari State Police dont really use capships (as far as I'm aware, no police forces do), so you'd be using a drake or wyrm light fighter. Those things are, IMO, one of the best LF's in the game - they have decent firepower and insane manuverability, most capships wont even be able to hit you.
Kusari Naval Forces allows the use of capships but you have to climb through the ranks, that could take time and is usually a frustrating ordeal, one reason I dont like player factions much.
The Hogosha arent really illegal, but they arent legal either. They work behind the scenes in Kusari, manipulating the government and fighting 'for the people'. They're pretty much stuck in CSV's until their black dragon is added to the mod, not even sure if it's approved yet or not. You could probably RP a hogosha background into using something as large as a gunboat though.
Last option is the blood dragons, one of my favorite groups in the game. They're considered unlawfuls by the rest of kusari, but their purpose is lawful... they're trying to remove the corrupt government system currently used in kusari and replace it with something more controlled by the people - like kusari was back before the current system. They're technically pirates, but they base their lives around honor and a code, unlike most others in Sirius.