How technically challenging is building(?) printing(?) these pieces? Presumably they need to withstand enormous amounts of strain. Can you produce an impromptu factory anywhere, or does this require sophisticated equipment that benefits from fixed installations?

It's a pretty complex and manual process. You need tons of space, and it's usually built with composites. It's pretty challenging to inspect them for flaws once they are built too.

Afaik, they are built in dedicated factories but usually on the same continent (at least!) as where they are going to get installed.

> shaped like calamari rings

... but why calamari rings specifically?