New autopilot on 2009 sailboat

[pacman]

The sailing boat is equipped with a E80 Classic MFD, S3G autopilot, ST-70 instruments, Wind vane, Digital Radar, AIS 500, DMS 30 and some other N2K sensors connected to the Seatalk NG network. There is also a Seatalk 1 network connected with the converter.

I am in the need to add a second autopilot for redundancy, going to make blue water sailing in a short time-frame.
The question is: which is the best model to add and what type of compatibility issues would I eventually face?

The current setup works just fine and I would like to keep the external ST-70 autopilot to manage the new autopilot. Which are the drawbacks if any?
Will I be able to setup a course on the E80 and enable the autopilot to follow it?

Thank you in advance for your kind availability