Short answer: yes, absolutely.
Before I begin: my personal philosophy is that the starter battery is sacrosanct. You never build something that will compromise it, because if all goes pear-shaped when you're out there, THAT is going to start your vehicle and get you home.
You have choices in how you manage the battery and coin makes a difference. The cheapest way is to use a
VSR to connect/disconnect the battery from the starter. This will basically be the same as you have now, except that your starter is protected from anything that consumes power from your second battery.
Your next step up is a DC-DC charger. My pick would be the
C-Tek D250S which also allows for solar input. No isolator or solar regulator is needed and it will charge the battery at up to 20A per hour.
You could use other variations - Redarc make an isolator that works, and allows you to override the disconnection when needed. Redarc also make a DC-DC charger.