Group of Bikes: Is 3x1 an option? I'm an RA for a dorm that is considering buying a number of bikes that would be owned by the dorm and lent out to students. I will be at least in part responsible for maintaining the fleet (about 10 bikes) so I was thinking it should have fewer things to break. I considered getting single speeds but I think students might want to be able to change gears from time to time (though there aren't many hills here).

I was thinking maybe a triple crank and single speed in the back might be an option. This would mean only a front derailleur so fewer parts to fix. Has anyone tried this? I couldn't find anyone online mentioning it. I think a 1x9 with a 34T chainring is the other option.
I don't think you can make a 3x1 setup work.

In order to have the chain change gears, there needs to be a mechanism to take up the slack in the chain. In a normal dual-derailer setup, the rear derailer does that.

You might be able to make it work with a chain tensioner, but I'm not sure if you can find one with enough range to do the job as well as a rear derailer.

Obviously you could do it with a rear derailer locked to the one gear, but that defeats the entire point.

A 1x8 or 1x9 would work fine, of course, since the only derailer is a rear derailer and it would handle the tension.

Another option would be to go with an internally geared hub (IGH). It's fairly common for "cruiser" and "town" bikes to have a 3-speed internally geared hub. That would give you most of the extra durability of a singlespeed drivetrain and allow for a very thorough chain guard (no pant rolling needed). Internally geared hubs often have a built in coaster brake, which would mean you'd only need a front brake. Even better would be a belt-driven internally-geared-hub bike (no chain lube!), but that requires a frame (at least dropout) built for it and would definitely be more expensive.