I started creating a Sisters of Battle fleet for the game 'Battlefleet Gothic' so I can use my favourite 40k army in that game against my brother.
the basic idea behind the backstory is that the ships are not warships and so don't have a lot of weapons, instead they rely on acts of faith to literally and miraculously burn heretic ships that get close and protect them from harm. The ships are just spaceborne Convents that recruite and train Sisters and don't have a actuel fighting purpose.
i have played around with creating BFG rules for Star Trek and Star Wars ships
this is all just a rough idea that I wanted to show people.