[stephenr]

You kind of can do that, but it's not a Vagrant feature, so much as a Packer feature.

Most of the Packer builders (e.g. virtualbox, parallels, VMware) support building from scratch (i.e. start with ISO install media and a blank VM disk) OR building from an existing VM.

So you could have a multi-stage Packer build pipeline that iterates step by step.

But I'm still not really sure what your workflow is. My company builds a series of Debian (and for a client, Ubuntu) base boxes. When debugging issues, 99% of time required is checking/fixing inside a running box. Once a solution is found, applying that back to the base box provisioning scripts (or preseed or even the packer config) and testing a build doesn't take that long.