You might find this interesting:
http://objectivebias.com/entry/formutilities-plugin-for-coldbox
With the form utiities set up as a plugin, you can name your form fields in such a way that they are converted into arrays or structs for you.
I don't use populateModel() that comes with ColdBox so I don't know if it will automatically populate composite objects, but that plugin shoud get you going in the right direction.
Thanks!
~Brad