It's a lot of messing with xml files, adding text and all sorts of that fun stuff. It is certainly no easy task for beginners or people that know very little about doing this stuff. For example I wanted to make a custom Star Destroyer hero with special hard points and what not, turns out that's an utter nightmare to create without having the right know how. To get what you want you'd have to start investing time into learning how to work with the games files and add abilities like the ones you mentioned for certain ships and what not. All I've managed to do with my time here with this awesome group is change values for units so that they cost less or take a shorter amount of time to build. I of course could be completely wrong with the difficulty however, as I'm not very good at working with the files myself, I'm just telling you my gut feeling.
Either way best of luck to you!