In theory much like a hard drive head floats on an air bearing over the platter it should be possible given enough development time and money to make a tape head that floats and never quite touches tape. I worked at a place in the 90s that had IBM floating tape transport where compressed air maintained some loops bouncing in channels to make sure the tape was never snapped taut and therefore stretched but I'm taking about actually floating a non-contract head which AFAIK has never commercially shipped for tape (although it would be cool to be proven wrong).
I was going to bring up how tape can throw oxide after a couple decades in storage but I suppose core could have dissimilar metal corrosion over the course of a century or maybe temperature cycles would stress and crack individual cores after a couple centuries unless kept at a constant temp. Also in theory non-archival core could exist just like non-archival tape definitely exists. So fair enough on that account.
except for tape
>The marketplace for eternally non-volatile low tech near radiation proof no moving parts infinitely rewritable data storage is roughly nil
incidentally google is the biggest buyer of tape in the world
>I would imagine given enough money one could find a way to 3-d print cores around taut stainless steel wires then fire the core ceramic, automating the process.
you are describing tape and it's predecessor wire recording. Rather than coat a wire in magnetic material they just used steel wire. They only use ceramic to make core because it's easier to fire it in an annulus than to punch out laminations that small