If you're still open to weapons upgrades...
Laser duration capacitor
Teaser
As our basic weapon, the Laser turret fires a short, concentrated bust of energy. Despite the upgrades, some of our scientists think they can upgrade the weapons system to give it a longer duration of fire.
Description
The Laser Duration Capacitor (LDC) module is designed to regulate, amplify, and store power from the weapon's main reactor. With the LDC, Laser-equipped units are able to fire a laser beam for nearly three times the duration with a slight decrease in firepower.
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I figured this better brought the Laser weapon to what modern lasers appear to be. They'd fry spiders pretty much instantly, but 2-3 of these units would be able to melt individual units quicker than without it. A range upgrade would also be nice for this system.
Minefield Adaptation Package
Teaser:
Historians have pointed out in military records that the application of minefields as area-deterrent weapons have changed the courses of war, and significantly altered the outcome of several battles. Our scientists propose to upgrade the Electrostatic Grenade launcher package to better fill this task.
Description:
The Minefield Adaptation Package is a simple replacement of ESG munitions with refined warheads. Unlike the older short-lived ESG modules, the newer munitions store their energy until expended by a vehicle. Although these ESG modules will not be able to recognize between friend and foe, they can now remain in place almost indefinitely.
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I wish ESG warheads could linger around longer, and one could mine chokepoints around a base. Perhaps giving scouts an upgrade to 'see' the mines could be an effective counter? And provide more of a use for scouts.
EMP Warhead
Teaser:
Repeated observation of exploding power plants has reported an EMP shock wave expanding from the destroyed facility. Several ambitious scientists have proposed a means to replicate this same massive ring by adapting a Starflare warhead.
Description:
Essentially using a weapon turret's own power source as a weapon, the EMP warhead, though expensive, replicates a smaller scale version of the EMP shockwave that disables several units in a small radius. However, friendly units are not immune to its effects.
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Why not? It makes something like the EMP missile available to Edeners, and Plymouthers have a means to get more EMP out there for their spiders. They'd be nasty as guard turrets as well. It also means another area-effect weapon, aside from the Acid Cloud and ESG.