I don't dry camp enough to justify spending money on mods, so this is what we do for a few days at the beach:
Use jugs of water for flushing to avoid running the pump. Also you can fill your tea kettle from the fresh water tank drain outside.
I don't use the 12V lights. I have 2 little $5 LED camping lanterns that run off of AA batteries.
If the trailer battery runs down enough for the fridge to quit I will use the jumper cables and the van to pump it up.
In case of complete 12V system failure, I carry a cooler to save the fridge food.