[LGM]

In any good weapon/size mod, in my opinion, the follow should be employed:

Differentiate Cruiser, BC, BB, and DN hulls with escalating tohit modifiers.

Tone down the weapon-mount efficiency to make smaller ships more feasible.

Find a way to limit the power of the talisman: more costly, treat as 10KT armor to destroy/defile it first, etc.

Make the Phased Energy Weapons weaker. 2 Dam per KT ratio makes this weapon very effective quite early in the game. I increased its supply usuage by 10 fold in my Mod, otherwise, I kept it the same.

Make the weapon research base numbers larger. 5K for most of them is ridiculously low. Who would ever deploy Null Space 1 when NS 3 is so easy to reach two turns later?

Make torpedoes cost effective. Some authors give them a tohit bonus.

I would suggest the following weapon efficiency: Low tech/Low cost weapons should do 1 damage per 2 KT of space occuppied. The best weapon Ratings should be 2 damage per 1 KT of space for a nice balance. Consider rating weapons within that range using Damage/Space/ROF to figure out rough efficiency. I would suggest treating ROF = 2 as ROF=1.8 for effiency so that they do not become to favored over ROF=1 weapons. You should lose a little efficiency taking all the damage upfront on the first round within range.

Make Crystalline weapons attractive. Suggestion: Better damage ratios or lower research base.

You have to tone down Small DUCs! 5:1 damage to space ratio for Sm DUC III is absurd. Extremely low tech/cost/space weapon with a very high damage ratio and it fires every damn turn. For good fighter weapons, make them research Sm APB, Sm Mesons, or Small racial tech weapons. Sm DUC III should be just a temporary deployment until they get something better.