If you're being anal about designations, those battleships aren't battleships anyway. Battleships were coined for the old ironclad ships that replaced the line battle ships. The dreadnaught classification coined in 1905 would be more appropriate for a ship three or four times the length of an ironclad. Really it's just a general classification that changes depending on who's doing the naming, and could loosely be applied to all modern naval warships, not one of our modern frigates are less than a match in firepower or durability to a WW1 battleship, let alone something from the 1800's.
Obsolesence in space. Conventional space travel is practically speaking, impossible. Unless of course you've created some form of inertial dampening. Going from thousands of miles per second, a rough estimation of the unit speeds, to a full stop in a second? Everyone on the ship just turned into a very thin film on the walls, assuming the ship itself didn't just experience its own implosion triggered nuclear blast. In such a universe where reality is either compensated for or ignored in such a manner, inertia is a relativistic problem that can basically be ignored. For balance reasons it's a neccessity that the biggest badass be the slowest badass, but it's not a physical requirement as it would be today if we decided to start an interstellar war with little green men and spent the next million years traveling to the nearest star. Of course, we could also be cute and say it's really taking several days to cross that gravity well and the game just advances at a rapid pace for convenience. In which case we're not really using anything resembling realism at all and all of the previous and following is pointless.
Another problem is the idea of a really big bomb. They didn't actually use really big bombs to kill really big ships. It was often a fairly small hole by comparison, something you'd also sink a significantly smaller ship with. You perhaps needed to poke a few more holes due to segmented hulls, not a real big deal. These futuristic spaceships aren't floating in water slightly below the density required to sink. A hole leaking atmosphere from a portion of the ship is a hole. They also have shields. Shields aren't an arbitrary concept, they are something that feeds off power. Your method of power generation is almost surely going to be limited by size in some fashion, so the size of the ship can scale directly with it's shielding. The armor, although less so, is also comparatively uninhibited. You needn't worry about problems like sinking, so mass is irrelevant. If you have a ship with 20 inches of armor and a ship with 200 inches of armor, the only difference is how big of an engine you need to push it, arguable considering the definite existence of inertial dampening. Weighing more doesn't pose any other problems.
Battleships have been antiquated by physical limitations of something that floats in water, and the technological limitations in defensive weaponry. We can kill them much easier than we can protect them. Shielding doesn't likely hold to that architecture though, it's an equalizing force that changes a battleship from a big, exceedingly slow target, to something that can have a hell of a lot more shielding and take one hell of a beating before even suffering damage. Being in space with inertial dampening, it's not neccessarily slow either.
For research... This damned leveling system really screws up the idea of sticking abilities in later research and just having them be big guns. What would they level before they obtained that research? Do you stick them at level 1 and keep them there till abilities are researched? It's a rather contrived setup to start with, and probably not improved by such a change. Many of the abilities aren't things that look like more advanced technology anyways, the range enhancements are akin to having radar. The Dunov and Akkan I would say have advanced, tech requiring abilities, but not the other three. Making them research requiring capital ships would make perfect sense. It only seems wierd having such early access to the other three because it takes equal effort to gain access to siege frigates, missile frigates and more for carriers, the smaller equivilencies. With armistice, I'd say the Akkan is worth at least eight or nine, without still five or six, and the Dunov with that shield restore(that's worthless on anything but a capital ship by the way,how about changing it to be an area effect on the surrounding ships if significantly less impressive magnitude?) is an impressive lifespan increase on your capital ships if not drained of antimatter continuously, probably worth more than the Akkan. Against this poor ai, four of those by themselves is the game twice over. Regardless, it's going to seem odd that the command cruiser is so high up the tech tree.
