> It's not like there is a mirror datacenter just two blocks away
Isn't that exactly what Availability Zones are for? They're physically separate[0] datacenters and each one contains a copy of each S3 object (unless using the explicit single-zone options)
It's also straightforward (although not necessarily that cheap) to replicate S3 objects to another region
Not sure about heat pumps, but in the UK at least there are a couple of companies that specialise in residential water cooled AC, e.g [0]. They use the cold water intake to cool down the compressor which sits inside the property
From a marketing perspective it’s not (as far as I’ve seen) driven by eco credentials, but by not needing planning permission - external AC compressors are not automatically permitted in the UK.