Well, your questions are pretty specific. But I have looked into the issue a bit, so maybe you'll find some of this useful for your cyber age.
Using real-world physics, it isn't tough to make artificial gravity using rotation. Centripetal acceleration =
rw^2 (using w=omega), so if we put a cap on the ship's rotation at 4 rpm as per Hill & Schnizter (1962) we only need a radius of ~55 meters for 1
g. Of course, with a radius that small you can run into noticeable weirdness (
e.g. gravity changes depending on which direction you walk or what floor you're on), and other researchers have suggested much lower rotation to prevent psychological effects; Hill & Schnizter even suggest 0.01 rad/s, requiring either a radius of 98 km or else a much lower apparent gravity. Since this is an rpg rather than NASA, you could probably get away with a radius of a few hundred meters - but you probably wouldn't want the spacecraft to be long. A spaceship with even a small 100m radius would be quite large at a length of 200m; wikipedia tells me that the Typhoon-class sub was only a fraction of that volume. The alternative is to make the ship rotate end-over-end, and then put living space in two drums on either side, and require transport between the drums through a brief zero-gee area.
For materials you'll want a mixture of metals and advanced plastics to keep weight down. Plausible weapons will be projectile based, probably using magnetic rails, so defenses may take the form of magnetic fields; these would be necessary anyway to deflect the solar wind. But non-magnetic projectiles would be undeterred by magnetic fields, so layers of hull reinforcement would probably also be necessary.
Weapons
can be lasers, provided that they are primarily ship-to-ship, since atmosphere will diffuse the beams; likewise ship defenses will take the form of smoke-screens and perpendicular mirrored panels to reflect beams back at the sender. Once some alloy is found that reflects across the spectrum, though, it's hard for me to imagine how lasers could stay effective.
Regarding propulsion, planets create deep, deep gravity wells, and it wouldn't be economically feasible to carry huge stores of fuel and burn them all over the solar system. So most merchant or exploration vessels would probably use low-energy thrusters and cruse through the
interplanetary transport network; passage on and off ships could take place in space stations or
space elevators. Only warships and colony vessels would carry out fuel-intensive maneuvers such as planetary landings or free motion throughout the solar system, with one likely exception being very light zero-gee scout vessels propelled using a solar sail. Larger vessels might have a few such scouts with their sails folded up in a hangar.
Given the vagaries of
n-body motion, current maps of the asteroid belts would be prized by traders passing between the inner and outer planets. And it goes without saying that trajectories would be carefully calculated by computer (or by aspies addicted to
the spice); any deviation would be expensive and nail-biting.
I could go on, but I have no idea whether these are even the kind of suggestions you were interested in. Maybe they'll stimulate someone else to post something, though!
References You Probably Don't Care About
Carl C. Clark and James D. Hardy. "Gravity Problems in Manned Space Stations." Proceedings of the Manned Space Stations Symposium, April 20-22, 1960, pages 104-113. Institute of the Aeronautical Sciences, 1960.
Paul R. Hill and Emanuel Schnitzer. "Rotating Manned Space Stations." Astronautics, vol. 7, no. 9, pages 14-18, September 1962. American Rocket Society.
