I am the developer for MWOSD and have been asked to add analog video OSD support for Ardusub.
I am not sure if these is much interest for this but thought I would share so you can be aware of what is available.
Here is the first cut showing some of the data available. Depth etc start after around 30 sec.
OSD displays are fully customisable for positions and features enabled / disabled. Different layouts can be selected using an RC channel.
Modes are displayed - circle/surface/manual etc. etc.
It is vary much aimed at aircraft, but most features are common and can be easily tweaked.
Uses minim style OSD like the minim Aeromax OSD.