I think there is a use for both too.
Don't add rubber feet if there is a chance they will fall off - nothing worse than a wonky turntable. Maybe you could provide a piece of non stick shelf stuff, or suggest customer buys or uses some for under the base. Actually the Ikea lazy susans have a rubber ring - they don't look like they will come unstuck, so maybe that's a better idea than feet/pads.
Maybe you could add notches in the edges, to mark 1/2, 1/4, 1/3, 1/6, 1/8ths (or whatever) of the cake easier. Like they have on the PME tilting turntable. Not sure what others would think about that, I guess everyone has their system to divide the cake equally for decorating when needed.