There is currently no support for deploying nodes using pre-install ssh keys as is required, for example, by EC2. In my github fork I have added basic support for this (I'll attach a diff as well).
An EC2 deployment using this patch looks something like this:
deploy_node(Provider.EC2_US_EAST, name=name, image=image, size=size,
deploy=deployment, ex_keyname='foo', ssh_key='foo.pem')
My main concerns are that I'm not sure if passing the path to the private key is entirely consistent with existing conventions, and this will break if someone passes in a NodeAuthSSHKey (although that was true before as well).