If you go back far enough, you'll need someone who knows how to make an RCE over AppleTalk.
Probably doable, BTW. Office (and home) networks were much less hostile back then.
Another issue with classic macos - cooperative multitasking is prone to system hangs
True. Once you overflow a buffer, you own the machine.
Fixing the security vulns in a non-networked computer would also be a lot less critical...
Probably not possible if you want to directly run a modern web experience on it. Classic macOS has effectively no memory protection.
Having an order of magnitude (maybe two) fewer lines of code goes a long way to having fewer vulnerabilities. Given the longer and more rigid development cycle and smaller attack surface, it's reasonable to think there are relatively few defects.
No doubt, but vulnerabilities aren't too much of a concern for a permanently offline machine, as something oriented toward focus probably would be.
For a writing machine, it would be preferable to keep it offline so security issues wouldn't matter.
Yes, but Wikipedia and Google are very handy. Addictive websites not so much.