[Beck]

Mines - Did they use mines? Or anything that could be used as mines?

For the time period, they do not use anything close to resembling mines. I can not think of anything period they could represent off the top of my head.

Fighters - Row boats? Is it possible to allow fighters to use the boarding attack? These would be high KT fighters, obviously, with a very large ship being able to carry around 4, total.

Unfortunately they can not use the boarding attack. Fighters could however represent gunboats. These were what amounted to large rowboats with a single gun mounted in the bow. Used mostly on large lakes they really weren't launched from large ships, but for game purposes I wouldn't see a problem given the small number that could be launched this way. You could also have fireships launched in this fashion or as drones. Its looks like you're towards having period flavor and not necessarily historical accuracy and given the tools you have in SE4 for making such a mod it is probably the only way to go. It broadens the choices you have to offer and the strategic issues a player should face.