Could possibly be handled by lxc-clone. See: http://s3hh.wordpress.com/2011/03/28/lxc-clone/
Haven't thought about this yet, but this seems relevant: https://github.com/turbosquid/lxc-clone-vagrant
Thanks! I came across that script a while ago but forgot to update this issue :P
Closing as it is not a feature that has had enough interest, I'd look into a PR though.
Hm. Any updates on this? Or a workaround? I need this... 👍
vagrant has built-in support for linked clones now, but it would require a bit of work to implement in this plugin. PR's are welcome.