Considering Time Capsule will have an IP address (I believe), it should be technically possible to access the storage disk from anywhere.
MacBook Air is fenomenal, but it has a small HD. If it could access Time Capsule remotely, there would be no need for any larger HD!!! And no way to forget documents, even if you don't have another Mac that must be connected 24/7 to the Internet to enable Back To My Mac...
Any hope for that?