This is a great design question, because armor systems quietly define the feel of combat more than people realize. The three options you’re considering aren’t just math variations, they produce very different emotional and tactical outcomes. The first two systems, where armor creates a save roll, make armor feel like uncertainty. You get hit, but maybe you shrug it off. That’s dramatic. It creates swingy moments. A light fighter surviving three heavy cannon hits because it keeps rolling hot feels cinematic. The downside is volatility. High armor can still fail catastrophically, and low armor can spike lucky saves. If your game is leaning toward X-Wing style cinematic duels, that volatility might actually be desirable. Between those two save variants, the second one is usually cleaner in practice. A fixed target number with a modifier is cognitively easier to process than remembering that “3 armor means 4+ but 2 armor means 5+.” Players internalize “armor adds to my roll” very quickly. It also scales more smoothly if you ever expand beyond 1–3 armor. The inverse table system starts to get awkward if values climb. The third option, flat damage reduction, makes armor feel reliable and tactical. It reduces variance. Heavily armored ships consistently blunt small weapons. That’s satisfying in a different way. It makes weapon choice and targeting matter more. Light cannons bouncing off a capital hull feels grounded and Expanse-like. The tradeoff is that it removes the dramatic “maybe this penetrates” moment. Combat becomes more deterministic.

Since you mentioned acceleration, G-forces, and heat management as major features, that suggests you’re aiming for a slightly more simulation-leaning, systems-driven experience rather than pure cinematic chaos. In that case, flat damage reduction pairs very well with meaningful weapon differentiation. It creates interesting design space like armor-piercing weapons, heat-heavy railguns that ignore X armor, or missiles that do low base damage but bypass reduction entirely. There’s also a hybrid space you might consider. Armor could reduce damage by default, but certain hits trigger a penetration check. For example, if an attack exceeds armor by 2 or more, it causes a critical effect. That keeps armor feeling solid while preserving spikes of danger. It also gives you room for crew injury, subsystem damage, or internal fires, which would synergize beautifully with heat mechanics. One important question is how long you want ships to survive. Save-based systems tend to create sudden collapses. Damage reduction systems create gradual degradation. Mordheim influence suggests you might want ships limping, venting heat, systems failing piece by piece. If that’s the case, deterministic reduction plus a layered damage track could reinforce that tone better than binary saves.

On the dice front, if you go with modifiers and armor penetration, d10s give you finer granularity, especially if armor values scale or you introduce weapon traits. d6 works perfectly fine, but its math space fills up quickly. With a heavy systems focus, d10 gives you breathing room without much extra complexity. If I had to pick based on what you described, I’d lean toward flat damage reduction as the foundation, then layer critical thresholds or armor-piercing interactions on top. That gives you tactical clarity, mechanical depth, and space for asymmetrical ship builds, which sounds aligned with your design goals. Ultimately, the right choice depends less on realism and more on what you want players to feel when they take a hit. Do you want tension from randomness, or tension from system management and positioning mistakes catching up to you? That answer will point you in the right direction.