Well, going towards generalities... if you want to go with a big vessel, start from an existing rock and start adding stuff. Big structural constructions are hard in that they take a lot of infrastructure to get everything in place and assembled, but starting from an asteroid or the like bypasses a lot of that. If you want to go towards the "incredibly tough constructed ship" side of things, go smaller, or start with a heavy base hull, or both. One thought that just occured to me is starting with a tanker car and adding reinforcement, armor plating, and or layers of whatever else. It's not as large and stylish, but it's easier to do by a lot, and from what you're saying this sounds like something of a reflexive impulse - a reaction to a bad experience done quickly to feel safe, and not even necessarily breaking any new technological ground or the like.
Star Ranger4's idea is interesting too, in a fighting back without fighting sense. But it's not to me to judge if that's directly appropriate for your character.
Star Ranger4's idea is interesting too, in a fighting back without fighting sense. But it's not to me to judge if that's directly appropriate for your character.