gistfile1.cs

public interface IAutoMappingConfigChunk
{
  void Configure(AutoPersistenceModel model);
}

// in AutoPersistenceModel
public AutoPersistenceModel WithConfigurationChunk(IAutoMappingConfigChunk chunk)
{
  configChunks.Add(chunk);
  return this;
}

// WithConfigurationChunks(assembly) etc...

// before compiling automappings, iterate configChunks and
// execute them against the APM
foreach (var chunk in configChunks)
{
  chunk.Configure(this);
}