By the way, so that no one can complain in the future, new warships will be rolling out in Valkian homespace. Not mass-production, but there'll definitely be an increase. Many ships are gone, exploring neighboring systems, so it's best to keep the home defense fleets up and full. Explorers probably won't be produced until there is an active war with someone.
And stealth isn't exactly a special drive. Draconians go full-blast with stealth on their Lightships, so that they are effectively, totally and completely, invisible, but space is massive. What is 'close' in space is too far to go with a bullet on the ground. Giant ships keep their distance; they can't afford getting too close. Space is too tricky to handle in to pilot that close. So, visually hiding oneself is really only needed if you're being a Lightship- where you're essentially coming right up to someone's face, blasting them apart with a powerful gun, and then fleeing.
The Battleship X could stealth itself, if it wanted to. It'd be much, much harder than a Frigate or even a Cruiser, but it could. If it sat at the edge of a system, and shut off all active sensors, locked in its heat and everything, ran silent, it'd be invisible. It'd be pretty damn hard to detect without getting in close. And the likeliness of getting in close to a single spot on a MASSIVE SPHERE, is pretty damn low.
Being unseen isn't fancy unless you're going in close, or even medium range- just shutting most everything down and deactivating all active sensors is all you need. Actively sweeping for things is revealing your position- to a passive scanner, it lets it know the source. So everyone sees you if you actively scan. Valkians actively scan- Draconians only scan if they think they can overcome anything, and lock on active sensors to a target to blind them. It's like laser lights, I think.
And plasma are like, generators that create a containment field, no? Produces plasma, puts it inside, and then jets it out? High rate of fire would mean overheating, and an EMP could possibly disrupt the field. If you're about to fire, or holding a shot, that'd essentially destroy that containment field, but not necessarily the systems, and blow up.