Bradley, what's your budget? Specific recommendations depend on how much you want to spend. Generally, a single coil guitar (fender type), and a humbucker guitar (Gibson type) should cover it for 95% of the guitarists. But do you really need to supply guitars? I get plenty of guitarists who come by my studio to jam who appreciate that I have some amps so they don't have to schlepp theirs. But they virtually all bring their own guitars. As for amps, a Fender, a Mesa, and a Marshall would, again, cover the bases 95% of the time. Or a modelling amp could cover all the bases. I wouldn't bother too much with stomp boxes. Most guitarists will bring their own. And I agree that Alembic guitars are probably not the best idea. It would be akin to supplying a stick shift car to someone who has only driven an automatic. There is definitely a learning curve to playing an Alembic guitar, more so than I suspect one encounters on the bass side.
Bill, tgo