Currently it is not implemented in our Vagrant provider, so that each VM is a full clone from its box and it is not an option to use linked clones instead. I've thought about linked clones as an additional option, but it requires a very careful approach for boxes, because we should to guarantee that box which is linked to any clone, will not be deleted accidentally. Anyway, it is a useful feature and I'll try to implement it in the future. P.s. By the way, pull request on GitHub is the best way to accelerate this process