Add a mapfunction to the chromosome implementations, which allows to create a new chromosome instance by mapping the internal data-structure, used by the actual implementation.

// E.g.
BitChromosome map(Function<? super BitSet, ? extends BitSet> f);
// or
DoubleChromosome map(Function<? super double[], double[]> f);

This method would be a more efficient way for creating updated chromosomes then the simply using the Chromosom.newInstance(ISeq) method.