DataTransformers make a convenient hook to adding probabilistic behavior into DataGenerator, either during post processing or during the search over the model.
If one desires to choose elements randomly from a set of values with weighted or uniform probabilities on the elements, any weighted choice code will work. Simply wrap the weighted choice code with a transformer that will set the appropriate variable to the chosen element.
The same idea extends readily to choosing numbers. Use any code that will generate numbers from your chosen distributions and wrap it with code to convert the result to a String and assign it to the appropriate variable.