HDMI Timecode and record flag
The compact and incredible quality Sound Devices recorders can receive via it's HDMI TC input which can also trigger the recorder.
If the TC and record flag can be sent over the HDMI along with other metadata info (which is on the HDSDI output and can be read by atmos recorders) It can make the mix pre a very viable double system recording option.
Sending this camera generated internal TC and a flag can also start and stop the recording.
Atmos recorders do this from your HDSDI HANC stream and embed clip names and other data in the file it records.
This functionality over HDMI would be a great extra for your user base. I have tested this through both the HDMI and the HDSDI ports (through a Blackmagic mini converter) but it can not used.
Perhaps SOund devices will give you the information of what signal their recorder needs for triggering and sending Timecode. The GH4 and SONY AS7 do this already.