I am about to start a new run on SS2 as a pure PSI character. I had been contemplating avoiding hacking, but I seem to remember at least once where hacking was required in order to progress. Can someone confirm if hacking is needed to progress/acquire any appreciable amount of cybernetic modules?

you can use psi hack, but it will be a while until you can afford that, so common sense says get hack 2.

Right, but I was wondering if hack is a skill that I need to have in order to avoid getting caught in an unwinnable situation.

I'd forgotten about Psi hacking, though, thanks for reminding me :)