Using an old GE Combo
I have had the 1966 version of this GE combo installed in my kitchen for almost 25 years now, and while it is not my primary washer-dryer it does get used a few times every month and it has never ruined a thing. It is true that older dryers and combs did have hotter drying temperatures available but people also had delicate clothing in the 1950s and these machines could do a beautiful job laundering them without any damage, { a quick hot rinse certainly will not hurt any clothing that was washed in hot water to begin with ].
I certainly do not see any real danger of fire with an appliance like this [ if I did it would not be in my kitchen ] older appliances had very little plastic used in their construction that will support a fire. I would however recommend staying at home when using almost any appliance that is this old, in addition to major appliances I would also include old radios, TVs, any small appliance that heats, etc.
I do share your concerns about energy use and would not encourage many people to use this machine as their everyday machine, however old combos in general are usually as efficient to use overall as a separate washer and dryer of the same time period.