I see Battleborn recently released some new batteries. They have a 270Ah
12V LiFePO4 battery that is approximately 23L x 7w x 13h. It would take some modifications to the armrests (probably complete rebuild), but I think you could get one in each of the sofa armrests for a total of 540ah. Thats plenty of power for most of us. Then the space under sofa can be used to install a Victron multiplex 3k. I have seen 400ah installed under sofa, it fits, but it is really tight.
https://battlebornbatteries.com/prod...e-gc3-battery/
If there are any 30' classic owners about to upgrade to lithium, it might be worth a closer look.