Just curious, with virtual server accounts why waste valuable dedicated IP addresses on each customer domain? There is some value to the serious programmer and SEO type of customer but most have no need for a dedicated IP address. IP addresses are too valuable to be assigning to each customer's domain.
It's not necessary and neither it's recommended to assign a Dedicated IP address to each customer domain. You can keep an option to select a Dedicated IP address and keep a charge for it accordingly. If a customer needs dedicated IP, an order will be placed after which you can request your hosting company to provide the IP address for the specific domain.