Allow customisation of the Village Transformer, by being able to specify block-for-block what each block should turn into depending on what biome the village is in.

Would you expect this as part of a structure's transformers, or as part of a general config system?
Either way, it might look a bit off if other structures in the biomes won't adapt too, don't you think?

Would you expect this as part of a structure's transformers, or as part of a general config system?

I'd expect it as a transformer.

Either way, it might look a bit off if other structures in the biomes won't adapt too, don't you think?

For sure. Then again, isn't it up to the person building structures to decide whether or not their structure should adapt to the biome it generates in?

I think this would greatly improve biome-specific structure building and makes it easier to create more dynamic structures, especially for villages in this case. I'm not entirely sure, but the way it currently works makes it so that one has to create copies of a structure with different building blocks for each biome (if they want to adapt their structure to the biome), right?