couldn't attach a picture, so go to this diagram to see sketch of wine glass cake concept:
start with a large circle of plywood at least 1/2 thick.
to it attach a central dowel
see this diagram: http://www.cakecentral.com/cake-photo_1420079.html
to the top of that attach a piece of masonite (pressboard) that is cut to size circle you want the diameter of the glass to be at it's base just as it starts to curve in to the stem.
for the curved part under the masonite -- either RKT or styrofoam
for the curved foot of the glass -- RKT or styrofoam
cake (the purple part) gets stacked just like any tier cake.
for really tall glass could make it a full 8" tall
could also carve it so it curves in like those balloon style wine glasses
I'd detail out the bottom circle of plywood so it looks like one of those round waiter's tray to complete the image of milady's wine being served.