Hi,
It will work if the magnet are big enough for the torque you want to handle. Obviously, with only 4 or 6 magnets, so far apart, this can be only a few Newton (in-lb) if your magnet are too small/weak/cheap.
Actually, if you are going for 10 or 20 watts motors, if might be easy. If you are shooting for KW, low revolution... This might needs some more try and error.
If you can reduce the GAP between the two plates, it will be best. 1/4 Inch will be a problem with smaller/cheaper magnet. But, try it.
You can do a search, on Internet, about "Magnetic Clutch". You may find some examples since their are many possible configuration: Plate, shaft and tube, Eddy current type where only one plate has magnets, etc...
Actually, you can build your own Electric Motor with the same principle use for the Disk-Brake generator. (Magnet and Rotor can be put in water proof fiber glass resin) However, to work, the motor need 3 phase AC. So, it might not be a cheap project.