I can foresee GSM of all things being a gun maker. But it'd probably be BSM for both.
As for cross class, since you only get two I'm suspecting GLD and THM. They'll need Provoke as a tank, so unless they end up learning their version of it they'll need GLD cross-class skills.

But who knows what changes they're making to the job system, including cross-class stuff. Without needing a base class, the new three jobs may not operate anything like our current ones.