After racking my brain, and occasionally feeling like I was banging it against a wall, I think I gained some insight into why More Luxuries doesn't always behave around other modpacks, though I can't really explain what the modpacks have to do with it.
I'll summarize in the hopes someone with more knowledge can figure out exactly what needs to be done:
The More Luxuries mod contains NewLuxuries_Resources.xml, and within that is the <Improvement_ResourceTypes> table. I used a sqlite viewer to determine that when building the game database, the luxuries were being added as expected, but the ResourceMakesValid and ResourceTrade values were 0, while vanilla luxuries had these both set to 1.
The mod contains lines like the following:
Code:
<Row>
<ImprovementType>IMPROVEMENT_QUARRY</ImprovementType>
<ResourceType>RESOURCE_AMBER</ResourceType>
</Row>
By adding two more rows as below, I was able to get it functioning as expected.
Code:
<Row>
<ImprovementType>IMPROVEMENT_QUARRY</ImprovementType>
<ResourceType>RESOURCE_AMBER</ResourceType>
<ResourceMakesValid>1</ResourceMakesValid>
<ResourceTrade>1</ResourceTrade>
</Row>
Again, I can't explain what modpacks have to do with this, as mine certainly doesn't alter these tables. I also notice that Nutmeg, Cloves, and Pepper seem to also have zero values for ResourceMakesValid and ResourceTrade, which I'll look into.
Hopefully further investigation can solve this issue for good.