Sorry for the delay, but I stumbled upon your comment just now.

So far the export API is pretty limited. It is designed purely to get a single collection’s documents out as efficiently as possible. There are no concrete thoughts yet about extending the export API into the directions you mentioned, though I won’t exclude that this is a future option.

Regarding the snapshotting:
For creating a snapshot of an entire database, there is arangodump. AFAIK it should create a consistent snapshot of the database even if data modifications happen while its dumping. There are some restrictions though: the dump won’t be consistent in a cluster and there might be issues if collections are dropped while the dump is ongoing. Finally, a full arangodump run may take a long time when run on a bigger database. But for smaller instances arangodump should be fine already.