For one-time dump of everything, that would work fine. For keeping in sync regularly, look at Dolt (google "git for data" for more solutions like this one, there are a few already).
I suggest using SQLite instead of the typical XML or JSON because SQLite is ready to be queried and easy to generate.
On SQLite, you can even store attachments b64 encoded. It will make it bigger and slower, but not so slow as trying to read a JSON or XML with the attachments inlined.