Karan,
I have only glanced at Rattle, but will take a closer look.
There are a lot of functionality we haven't brought into red-R yet. We are working on creating a more robust framework, so functionality can easily be added.
Modelling is something we do regularly, so I think Kyle has already have create some basic widgets. We will try to add new functionality to the the red-R updater regularly.
Anup