I'd love to see something like this.
I started a bug a while ago for a vaguely related feature suggestion:
Bug 31410 - Subscribe to remote VCard vcf as address list
Being able to subscribe to a remote address list (vCard file) would be amazing.
In the same way you can subscribe to a remote calendar (ics file).
That would be awesome for us as it would mean people would be able to send to our various customer lists held in our intranet database (apache/php/mysql) straight from Zimbra