For several years I've been playing around with something like that as a side project — see http://www.CommonDraft.org http://www.CommonDraft.org (which isn't e

For several years I've been playing around with something like that as a side project — see http://www.CommonDraft.org http://www.CommonDraft.org (which isn't especially pretty; I'm in the middle of refactoring it to make it more Lego-like).