The problem is that almost all weapons use a high slot. Battleships have no secondaries. Now, you could rig a Rohk, for example with 6 railguns and 2 anti-frigate blasters for example, this appears to rarely be done.
One reason is you lose 25% of your long range guns, the other may be that the small blasters just aren't worth a high slot on a BS.
It's kind of like the early dreadnoughts with inadequate secondaries, but lots of big guns, versus the late pre-dreadnoughts with a few big guns and abundant secondaries.
Perhaps if new modules were developed for battleships, like a "quad-mount rapid fire blaster" with the same requirements as a big gun turret, but the combat characteristics of four small blaster turrets.
Also, there could be adjustments to warp disruption and webbing.
For example, a battleship might have 3 warp points as a base making it harder to shutdown it's drive. And webbing might be factored against the mass of the ship, so sure, my small webber might stop a frigate dead or slow a cruiser significantly, but the battleship might just drag the webber along with it. Capital ships might not even notice a frigate web.
Some modules scale with ships while other don't seem too. Perhaps a battleship could mount a resource hungry warp core stabilizer that adds several points. Or a warp core disrupter with a much larger effect, i.e. points, range and perhaps area of effect.
Of course, it is always important to carefully adjust things so as not to tip balance too far the other way.
Torpedo boats in the Russo-Japanese war could not risk the numerous secondaries of battleships in daylight. Their successes were at night against unsuspecting or beaten and scattered foes.
