Can you add a trait that changes ocean plot yields?

[ArgonV]

Hola my fellow modders

I was just messing around, trying to create a custom naval civilization, with the emphasis on coastal cities. I therefore wanted to give them a bonus yield on ocean squares, with several buildings to improve upon this. However, I can't seem to get this to work. Here's the last thing I tried:

<GameData>
 <Traits>
  <Row>
   <Type>TRAIT_COMMERCE</Type>
   <Description>TXT_KEY_COMMERCE</Description>
   <ShortDescription>TXT_KEY_TRAIT_COMMERCE_SHORT</ShortDescription>
  </Row>
 </Traits>
 <Trait_SeaPlotYieldChanges>
  <Row>
   <TraitType>TRAIT_COMMERCE</TraitType>
   <YieldType>YIELD_GOLD</YieldType>
   <Yield>1</Yield>
  </Row>
 </Trait_SeaPlotYieldChanges>
</GameData>

I'm guessing it's because there's no similar trait in the game and making one is a lot less simple than I thought it would be

I could of course come up with a different way of bolstering sea resources (like the lighthouse and seaport already do), but I was still wondering if this really can't be done or if I'm just not seeing something here.

Any help would be appreciated.

[dmieluk]

I'm not experienced with civ modding, but for what it is worth, I had a look over the tables, and I couldn't see a natural way to do it either.

It seems you might be able to make a trait which alters strategic resource quantity dependent upon terrain, but not tile yields.

You could make a unique building which cost 1 hammer and has the effect you desire, but it is a very inelegant solution.

I'd be very interested in seeing if an experienced modder has a way to do this.

[ArgonV]

Yeah, that was my back-up idea; give the civ a free building that provides the bonus.
I was thinking of creating a maritime Civ that profits from having a few large cities, instead of a lot of smaller ones. This would fit with that development idea