Well, you could do a fresh fruit plate. That would fit the low-carb bill.
I would not take a chance with a synthetic sugar substitute in cheesecake. You risk ruining the structure of the cake, and having the chemical after-taste, which will then ruin your reputation as a baker who makes delicious things. On the other hand, stevia might work. Stevia is a natural sweetener derived from the leaves of a stevia plant. It is hundreds of times sweeter than sugar. In too high of a dose, it is cloying and has a funny, long-lasting after-taste, sort of herbal (some people describe it as woody). I have never used it in baking, and I don’t plan to, but maybe it would work if you’re feeling experimental. It is not approved as a food additive by the FDA, so you have to look in the dietary section (where the vitamins and bee pollen are kept) of a store like Whole Foods.
People are funny. Asking for a low-sugar dessert is sort of like asking for a low-protein steak dinner.