For my prototype, I am seeking to break the world record for an uninterupted stay beneath the water. (69 days set by Rick Presley).
I am looking at microwave ovens for cooking and maybe even MRE's (Meals ready to eat.)
Appliances used for RV's based on a 12 volt system is what I am looking at.
Same with the sewage. There are some excellent RV toilet systems around. The one I have chosen is a cartridge system.
Quite simply, fill it up and then replace it. (reuseable). Then top side support crews would remove each cartridge to dispose of in surface side systems. (flush it.)
The beauty about all this is that it is all "off the shelf" tech and quite affordable.
As you can imagine, the RV market is huge and many excellent products are available.
To try to counter condensation, it will be routine to purge an on board compressed tank to "flush" the ambient atmosphere out each morning. I am also interested in O2 and CO2 trade offs by using onboard hydroponics.
Yes, very exciting stuff. Well, to me anyways.