vagrant-s3auth | Vagrant plugin for private , versioned boxes on Amazon S3 | AWS library

I'm trying to provision a vm using vagrant's ansible provisioner. But I have two playbooks and both need to use different ssh users. My use case is this, I have a pre-provisioning script that runs under the vagrant ssh user that is set up by default. My pre-provision script then adds a different ssh user provisioner that is set up to ssh onto the VM with its own key. The actual provision script has a task that deletes the insecure vagrant user on the system so it has to run as a different ssh user, provsioner, the user that the pre-provisioner creates.

I can not figure out how to change the ssh user in the Vagrantfile. Example below is how far I've gotten. Despite changing the config.ssh.username vagrant always sets the ssh user to the last value, in this case provisioner and that doesn't authenticate when running the pre-provision script because it hasn't been created yet.

Can I override the ssh user somehow? Maybe with an ansible variable itself inside the do |ansible| block (below)?

Is what I'm trying to achieve possible? It seems so straightforward I'm shocked I'm having this much trouble with it.