Ok here's my take on it.

If you need a zap stopper then you should rewire your system.

I see 1 or 2 boats every year that has problems because someone turned
off the switch while the alt was running. When I get finished it
doesn't matter what they do with the switch as i try to murphy-proof
the system.

The output of the big alternator should go direct to the big bank of
batteries. The sense for this alternator must go back to same bank of
batteries.

Now you can use the switch to combine the banks have more then one
switch to do other things with, have a battery combiner in curcuit or
even an isolater to auto slow charge the engine banks (at main bank
voltage minus isolater drop).

Why are we having this didcussion if your boat is wired up right you
need no zap stop.

The engine manufacture can not do it right as he has no idea how your
banks are hooked up he can only put alternator output to starter. You
must wire it up right.