Warfare 3? Ricochets and hypervelocity fragmentation.
The new weapons introduced in Warfare 2 bring about an interesting new dynamic of penetration vs splash damage, though it raises a new problem: railguns are universally good against anything (except asteroids) - small ships get shredded in one shot and flung, and both large ships and stations can have critical systems shot out even through substantial armour.
I propose two solutions, to improve the survivability of well designed smaller vessels and of stations also:
- Ricochets: Modern tanks have been in an arms race with armour penetrating ballistics since time immemorial (okay, since World War I), and the main ace up their sleeve today is sloped armour. Projectiles impacting this armour typically do so at a shallow angle as a result (assuming they're not fired from above,) and are deflected, causing minimal damage. This also allows armour mass to be reduced, resulting in a lighter, more agile vehicle; the same can apply to spacefaring vessels. Sloped armour could be employed in strategic locations in lieu of heavier plating, keeping small vessels nimble; however, consideration should be taken into where incoming munitions will ricochet. As with tanks, you want to avoid deflecting the rounds deeper into the structure and creating "shot traps".
- Whipple shields: Modern spacecraft and installations, such as the International Space Station, rely on a lightweight - and low density - solution to hypervelocity debris: several thin layers of material spaced out from each other. Useless against regular bullets and shells, Whipple shields stop hypervelocity impactors by using their kinetic energy against them: the impact against the first layer vaporises the projectile and spreads it out, allowing subsequent layers to absorb the energy. Lower velocity projectiles, such as conventional bullets and shells, do not have the kinetic energy required to self-vaporise and would thus pass straight through; to make use of it alongside conventional armour would incur bloat, suitable only for static installations or already particularly large vessels.