Been going through this myself, and loving it; I grew up with Freespace. The UEF using overwhelmingly ballistics as their primary weapons, research that boosts Gauss, autocannon and railgun-type weapons would be most logical. The usual; things to boost weapon refire rate, damage, maybe even a DoT like the Mazra dreadnought's incendiary ammo ability. Precise details and boost types can be assigned later. I'm sure I can come up with a few examples. Let's see...
Damage boost Level 1 - Depleted Uranium slugs
Increase the weapon damage of all autocannon-based weapons.
Refire boost Level 1 - Modular magazines
By standardizing ammunition storage and loading mechanisms, ti is possible to achieve a quicker firing cycle for our ships' gauss-type armaments.
Damage boost level 2 - Gravitic coilguns
By modifying railguns and gauss weapons to use gravitic plating instead of electromagnets to propel a slug, a significant damage boost is gained.