The Plasma Cannon is great. All hail the plasma cannon. It's got a great sound (THOOOM), the animation is top tier, I like the swivel effect when it tracks a new target, the whole thing is just great. Only real complaint is that the shot fired looks exactly the same as regular plasma rounds. Not really a sense of "this came from a big gun" in it.

The Heavy Rocket Launcher and Solid Projectile, on the other hand, could do with some polish. Now granted, like 90% of my gameplay experience has been from Cravers, so I haven't seen much of the designs that exist. But for Cravers, the Heavy Solid Projectile is basically an upscaled regular Solid Projectile, and that's kinda boring. It's got a single barrel and both the sound and bullet trail is identical to the regular version. These two facts don't mesh for me. If it has a single barrel, I'm expecting more of a "Thud, Thud, Thud, Thud, Thud" sound to come from it when it fires, not "BRRRRT". With the Thud and the barrel, I'm also expecting a slower rate of fire during animation. The whole thing looks like an autocannon to me, and the fact that it doesn't behave that way is mildly disappointing/disconcerting. 

An alternative to changing the sound and animation (because I'm pretty sure the Devs don't want to mess with the guns that way quite yet) is to change the design of the gun itself. Give it more barrels. Make it rotary, like a chain gun. I can buy that sound/rate of fire from a giant minigun, plus it also justifies the twin ammo packs linked to it. A radical change would be to turn it into a shotgun.

For the Rocket Launcher, I'm really not sure what to say, aside from "It fires one rocket, and that rocket looks completely boring". It could fire multiple rockets, like an MLRS, but that feels like not quite what the Devs had in mind. It could be a really big rocket, and that feels closer. I feel like the Tier 4 rocket design fits really well here, like you could just increase that projectile size by 80% or something, and then I can buy it basically one-shotting a pirate cruiser. Those things just look like they hurt. Can't really say the same for the Tier 5 acrobats.

Third option: Cluster missiles. Have that one rocket split into other, smaller rockets.

I've got no data on the Beam of Death. Feel free to put your opinions on its design in the comments, along with your opinions of everything else about this post.

Side note: Somebody did a post on strategic materials and how they affect weapons, and it eventually migrated over to a topic about applying materials to modules in general, with a subtopic of hybrid modules. I would be super excited if this became a part of that, like adding Adamantian and Titanium to a Heavy Rocket Launcher turned it into a really big cluster missile, or Hyperium and Anti-matter on Solid Projectile turned it into a laser shotgun.