We migrated a site to MarketPress and were shocked to find

We migrated a site to MarketPress and were shocked to find out that we couldn't add coupon's to specific products as this is a basic piece of functionality for eCommerce systems. Our client refuses to launch the new redesign until this feature is implemented.

Is this feature planned in a future release? If not, how much would it cost to pay for this feature?

Or only other option is to update the plugin ourselves and break updating which is something we don't want to do.