The multi input multi output features described above for combined transactions appear to describe how to handle farming rewards in a secure way.
Spitball 2: a) If initial dbcs are created and seeded throughout the network, then b) a farmer (or elder?) could combine 1 with proof of a valid storage/retreival to c) get the dbc reissued with a portion of it equal to the current farming reward and then transferred to the farmer.
The process is a “Safe Contract”, but it also bears resemblance to classic safecoin by analogy.