Multiple Options with Squarespace ECommerce

I have a 99designs client that has selected a Squarespace Business Package (fully integrated ecommerce) — I know how to set up his services, but there are tons of addon options. His is an auto detailing service — basic, standard, premium detailing — but with many addons (buff waxing, clay bar, scratch removal, acid wheel wash, headlight restoration). All of these are available AFTER you select the car size (coupe, sedan, midsize, suv, full) — and at different prices. Anyone? Squarespace isn't ready for these types of options — what to do?