im not currently playing with mods yet but what might make a better balance would be something like 10% of max hp but im not sure if you can do that

a flat bonus is nice for smaller ships but becomes moot for larger hp ships
a % is going to be worse for smaller ships but pay off for larger ships ..

ehh 50/50

Well, I had also did a % and flat module... alas, it turns out my mod doesn't work at all.  I suck.

Anyway, in xml, the example I used was for the many modules which increase the attack or defense of nearby ships.  For instance:

<Stats>
<EffectType>BeamAttack</EffectType>
<Scope>AreaEffect</Scope>
<Target>
<TargetType>Ship</TargetType>
</Target>
<BonusType>Multiplier</BonusType>
<Value>0.1</Value>
</Stats>

In my module, I had written for one module:

<Stats>
<EffectType>TacticalRepair</EffectType>
<Scope>AreaEffect</Scope>
<Target>
<TargetType>Ship</TargetType>
</Target>
<BonusType>Flat</BonusType>
<Value>4</Value>
</Stats>

And for another 

<Stats>
<EffectType>TacticalRepair</EffectType>
<Scope>AreaEffect</Scope>
<Target>
<TargetType>Ship</TargetType>
</Target>
<BonusType>Multiplier</BonusType>
<Value>1.0</Value>
</Stats>

Neither module, however, has any apparent effect on repair rates, though.  I'm not sure why, either.  I tested the Energy Magnification module and sure enough, the beam weapons get boosted.  But the tactical repair does not.  I wonder if it is just listed as a valid string... 

The effect TacticalRepair is used during battles. For repair outside battles the effect StrategicRepair should be applicable.

However the fact that an effect exist does not mean that it can be used for a given scope and/or target, therefor the only way to check whether it works is by trying it. So no guarantee that it will work.

I made a ship component mod that worked in Beta 4, but crashes the game in later versions of the game even while the syntax, definition and context are correct. The only combinations of effects, scopes and targets that are supported are the ones SD use. Hence let the user (of such a mod) beware.

Does this still work? For some reason I cant get it to show on the module list to build it.
I have a military starbase and the tech.

Actual mod file is in the path ..\Documents\My Games\GalCiv3\Mods\ShipRepair - Starbase Module\Game

so as you can see , I have the right folders in the right order etc.