You can clone with
HTTPS or Subversion.
I don't know if you feel this is technically easy, or worth implementing, but I thought I'd make you aware of a misunderstanding I encountered; I posted a question regarding it (and answered it myself) on stackoverflow:
Using the --reinstall flag with cabal-dev
I posted a response on SO: http://stackoverflow.com/questions/7451296/using-the-reinstall-flag-with-cabal-dev/7478072#7478072
re: the feature request --
I think that would be a good feature, but I'm a bit intimidated by the number of questions that arise; eg:
My gut reaction is that it would be easier to address the concern at a higher level, possibly by having a 'meta-project' description somewhere (which is what a lot of cabal-dev users have adopted, although I don't believe there is a standard practice for this yet. I've heard of many shell scripts that have been created to establish sandboxes.)