By 4 terminal disconnect you're talking about something like this?
http://www.rallylights.com/all/elec...y-master/tt061-battery-master-switch-fia.html
As it happens this one has two sets of low current contacts, so both the ignition and the alternator's exciters could also be switched.
In the case of the car that I'm about to wire the guy has one of the old school type battery kill switches with the gray pot-metal lever so when I said "it won't work" I was thinking specifically of that car and not of the bigger picture. My bad.