If we are able to copy entire rules, why not copy data elements as well? This would make migrating between properties a lot easier.
I'd also like to have the ability to copy the entire properties. Here'a a scenario:
When we deliver analytics for our clients we internally work on 2 or more environments, and then clients have their own internal environments as well (usually UAT, Staging and Prod). DTM by default supports staging and prod for one web property. Now if we could copy the entire properties we would probably have one property for our development needs (inside which we would have staging for development and "production" for testing) and we would simply create a copy of that property to support client systems (and then staging in that property would be used for clients for testing and production for live servers) - iniside that property we would only change the delivery options on embed tabs.
I think those abilities would be crucial to make the maintenance of DTM a lot easier.