BSF, given it's immense customizability, is better at realism than many other space-based games I've seen. Just use the MST3K Mantra, or incorporate realism into your designs as much as you can(take help from here
). Here's my take on things:
Real lasers in space would be invisible - which would mean that all BSF beam weapons would have to be some form of particle beam. Electron beams and heavy ion beams to be more precise, since I doubt neutron beams would glow like that either.
Blasters, particle guns, pulse guns, etc would just be particle beams firing short bursts that appear as "projectiles" - though if you want to make them more realistic, they'd have to be damn friggin' fast projectiles, much faster than ballistics.
Of course, both ion/electron beams and "projectiles" would be short-ranged weapons, due to electrostatic repulsion or defocusing caused by neutralizing them.
Ballistic Weapons & Missiles:
The ballistic weapons are ok, though. Mass drivers(railguns and coilguns) firing kinetic slugs are realistic enough. Bigger guns would fire fast-moving, high-damage shots, while smaller guns(preferably on Gatling-style rotary assemblies) would fire faster, but their shots would be slower and less damaging. Explosion radii can be created by using slugs fitted with an internal explosive that causes them to disintegrate into high-velocity shrapnel, like the flak gun.
Missiles would be the most realistic stuff you get. Though the stylistic side-launching missiles seen on so many ship designs would have to go, due to obvious Delta-V considerations(unless, of course, your ship is a broadsider). Missile damage would be based on whatever you decide that you want as your warhead - nuclear fusion, antimatter annihilation, shaped charge, kinetic impact, kinetic fragmentation, your choice.
Unguided rockets(like the HV Rocket Launcher) would be cheap spammy weapons with a higher firing rate than missiles, but bad accuracy.
Ballistics and unguided rockets would have unlimited range due to the lack of substantial friction, which allows them to keep going with whatever kinetic energy they were imparted with. Missiles would have a long, but limited, range - limited by onboard fuel supply needed for maneuvering and tracking their targets.
Invincibility-inducing deflectors are pretty damn unrealistic - real shipboard electromagnetic fields or cold plasmas would only limit the damage caused, and only work against particular types of weapon.
Armor is ok. Armor is armor. Slabs of stuff you put on your ship that takes damage instead of your ship until it gets entirely blown off. Ablative armor, Whipple shields, composite laminates, plain old steel, etc. Whatever you want to call it.
Point defenses can be included in the weapons stuff above - the particle gun would fall under the particle-burst "projectile" section, the point beam would fall under the particle beams section, the flak cannon would fall under ballistics, and the PD rocket launcher would fall under unguided rocketry.
The Rorschach module would be a pod that emits a very strong electromagnetic field until it runs out of energy - a field that would be able to bend the charged electron/ion beams mentioned above.
The Nano Matrix could be justified to advanced hull-structure and armor design and/or advanced nanotechnology. High tech, though not impossible.
The Impeder... I dunno. It's unrealistic, plain and simple, like the deflectors.
As for top speeds - those can be self-induced speed limits to conserve fuel for maneuvering, decelerating and other velocity-changing actions in the future. You don't want to waste fuel in space accelerating more than you need to.
For turning, you could use maneuvering thrusters or a thrust-vectoring system on your main engine. The thrust-vectoring would be less maneuverable, but maneuvering thrusters would be more vulnerable to destruction. A combination of the two would be the best, IMO.
For ship design, you would want to have all your weapons(except maybe for guided missiles) to be on rotating turrets, you would want armor around your ship's critical systems(like thrusters), and you would need big, unarmored, vulnerable radiators to get rid of waste heat in the insulator that is space. You could implement stylistic solar sails that double up as radiators, provided the sail section itself is fragile and has some armor in front of it to protect it.