I've thought about this issue but came to a slightly different conclusion. I'm almost ready to finally install a Bluetti AC200 in my 2019 passenger van conversion.
1. I have a 1000W inverter connected to the CCP to charge the AC200 while driving. The AC200 can be used to power the 12V house loads because it will be simultaneously charged by the van while driving. I ran wires to the roof for solar panels. It will be easy to add 200W of panels later, if this is needed.
2. The AC200 has a parasitic loss of approximately 10% of the battery capacity a day, when the DC output is on. It also losses additional power for the 12V house loads. I will most likely drive the van every day and can charge the AC200. The AC200 should have enough capacity to power the 12V house loads for at least a couple days. I only plan to rarely turn on the AC200 120VAC inverter. When I use the 120VAC I will need to monitor my AC200 battery level.
3. The AC200 has two DC outputs. It has a 12V/10A cigarette lighter output and the main 12V25A output. I'm going to wire these two outputs to separate Blue Sea 12V fuse blocks. This allows me to balance the 12V house loads by changing the loads that are connected to each fuse block.
4. My bigger concern is how to power my 12V house loads, when connected to shore power. This could be at a campsite or when parked in my driveway. I found that my local Goodwill often has Microsoft XBox power supplies. Some of these power supplies output 12V/17.8A. Note: you need to connect the red (5V) wire to the yellow (12V trigger) wire to turn on the 12V output. You can google "xbox power supply hack". I want the option to use two XBox power supplies to power my two fuse blocks when I'm connected to shore power. The XBox power supplies are pretty high quality but I can always source different power supplies.
5. I'm building a box with a rotary switch to choose between connecting the two fuse blocks to the two AC200 DC outputs, the two XBox 12V power supplies, or off. That way I can turn off the AC200, if I want, when connected to shore power, and still power the 12V house loads. I would mostly use this when I'm parked in my driveway at home. You could also use this same type of switch to connect the fuse blocks to the van battery. I will have this option by changing how some PowerPole connectors are connected.