First off, when the dealer says you "require" power assist with the Suzuki dual prop engines, I suspect that what he is really saying is that the steering feel would be very heavy otherwise and you would want power assist, not that it is actually necessary for the installation.
I have a NavPilot 700 and Safe Helm 2. I have a Sea Star power assist unit in my Teleflex hydraulic steering system that was already in place when the Furuno autopilot was installed. Just out of curiosity, I cut the breaker to the power assist pump and then enabled the power assist on the autopilot. It seemed to function more or less exactly the same. At the dock with the engines off, when I turned the wheel I could hear the autopilot pump run (it was in standby and thus should not have been running at all).
It may be that your dealer is not familiar with the Safe Helm or the Furuno autopilots because he is proposing that you have a duplicate parallel system. The only caveat is that I am not familiar with the Suzuki "fly by wire" control system and it is possible that it is somehow linked to it and that is the reason but that doesn't make a lot of sense if you have a conventional hydraulic steering ram and not one of the new electric drives.