Oh... yeah. It is a good idea. Your frame likely has horizontal dropouts, which are necessary for an easy conversion. You need to measure the spacing between the rear dropouts - it will probably be 126mm - and find a hub with the same over-locknut-dimension, then build it into a wheel of a rim that is a size that will work with your nishiki (27" or possibly 700C). Then you may have to change the crank or bottom bracket to get proper chainline. Then figure out a way to route the cables, and you are off to the races!