I wouldn't use just a saucer as it doesn't really provide the natural style of running.It's not good for most hamsters as the only wheel,but it does make an excellent toy if you have the space which with a 100 x 50 to 100 x 100 cage should be no problem at all
A lot of the reason flying saucers aren't that great is they do cause side arching and as said before they are not offering a natural style of running.This means that you would still want a proper upright wheel before even thinking about getting a flying saucer.