My niece has asked me to make a 2 or 3 tier cheesecake using wine glasses as a separator. Is this possible with cheesecakes being so dense. I worry that they would collapse[/i]

Why not use five wine glasses inbetween the tiers?
Four on each "corner" and one in the middle for extra support.

HTH

You would need a clear flat glass/plastic plate under the wineglasses, that sits right on top of the cheesecake.

But I wouldn't do this anyway. Cheesecake is HEAVY stuff. You might get away with a 6" cheesecake on top of a 12"--I mean that the 12" tier won't collapse while it is out of the fridge waiting to be served.

Instead of stacking them, why not persuade the bride to have oversized clear separator plates, so that the wineglasses are sitting around the edge of each tier on plates and not on cheesecake? The cake will look like it is floating on the wineglasses, but there will not be any weight on any of the cheesecake tiers. You can tuck a little flower into each glass...

But you are also looking at the investment of the cheesecake pans in 2-3 sizes, right?