Ready meal around 10 minutes at 750 watt output so 1 kW input so around 85 amp at 12 volt, so around 20 Ah used out of battery for 1 ready meal so yes theory can work, but the problem is recharging, we found with the narrow boat over night lights used very little from 3 x 180 Ah batteries but charging took time, and it needed a recharge time of around 12 hours to fully recharge, but we would only cruse for 8 hours, it is charging the battery which was the problem, even with stage chargers slowly the battery would become more and more discharged, so once a month my so needed to find some where with a hook up so he got around 16 hours extra charger with the 8 hours there and 8 hours after he got around 32 hours charging which would bring the batteries back up.
So you would need to be able to charge batteries over night as well as on the vehicle, we don't drive for anything like 8 hours, caravan uses have found solar panels are far better than split charging even using the sterling pulse inverter charger, problem we realised is cost, yes with solar panels and stage inverter charger we could maintain the caravan leisure battery, but it was for the amount we used the caravan cheaper to use sites with hook-up. The battery only really needed for motor mover.
We have considered an inverter generator for the odd time we are not on a site with hook-up, but in the main we use gas, we need a battery to pump water and for lights, no gas lights in modern caravan, and for ignition of fridge and central heating fan, and water heater ignition so we do need a battery, a 75 Ah will last us with care around 3 days, lights is the big drain, I have a very small inverter around 150 watt which will work PC, and also one built into the 12 Ah jump starter, but rarely used, the 12 Ah jump starter will charge from cig lighter output, so that is out back-up, once main battery exhausted that will keep things running until we find a site with hook-up.
But look at small inverter generator and compare with our jump-start pack, and not much difference, inherited jump start pack, when it goes will replace with inverter generator.