You can't change your CPU without losing the data in RAM (unless you are on zOS), and I think that's a precedent which people are ignoring.
Imagine a hardware architecture which considers NV-RAM as a very large and safe cache, and software which understands that.
This would be great for things like a (huge) RDMS which traditionally requires tables and especially indexes to be in RAM. Suddenly you can get adequate performance on multi-terrabyte indexes, and providing the software understands the storage hierarchy there is no explicit rebuild needed - the data is also stored on spinning rust and on a WAL maybe on a SSD, and will be reloaded into NV-RAM on read.
What type of usage am I missing where losing/having to do an offline rebuild of your data would be acceptable during a hardware upgrade? NOVA seems to be aiming to address the recognised issue by overprovisioning (which I disagree with but such is life). I don't really understand your argument.