Hi Todd, Thorleif,
Thanks for the replies; and yes that seems like a great idea; different light sensitivity/angle and/or focal lengths on the second camera - some combination making it easier to manoeuvre the ROV or see a different angle; such as Thorleif's suggestion for tether management is a great one too. (perhaps ideally eventually we'll have maybe 4 cameras or so!)
Having yours connected directly to the battery is an excellent idea too! - so you get live feed off of this (to QGC)?
I would be very interested to know your set-up if you're keen to share pic or description of it!