By replacing the emergency start solenoid wt. a battery separator (Shure Power, Inc., 100 amp, $75) makes the whole situation much easier in such a failure and makes every day operation and storage easier. The separator closes when the voltage raises to 13.1 volts on either the chassis or house side, thus regardless of the charging source, all batteries are charged.
When in storage and connected to shore power all seven of our batteries are maintained by the three stage converter/charger.
When dry camping, running the generator, likewise will charge all batteries.
When on the road, again all are charged without the voltage drop normally introduced by the isolator.
Wt. the alternator out, you would still have to do as you did in order to back feed the chassis when the generator was not running.
Jim