Why advertise one pot if it damages the machine?
There are plenty of frying pans/skillets on the market that claim to be built for years of heavy use, but you'll be lucky if you can make any of them last more than a year or two.
I imagine there are people in Japan who use regularly use their rice cookers for one pot and baking and simply expect to buy a new machine every couple of years.
If you want to go ahead with using a cooker for everything, perhaps the best approach is to find a machine where you can buy (or at least order from the manufacturer) a replacement/extra pot at the time you purchase it. A year or two later the spare bowl will almost certainly be obsolete and impossible to find.