CakePHP script feature adding (Group Buying Site, Agriya)

We are currently using Agriya's well written cakephp GruopDeal script for our group buying site. We need to add some add-on feature on top of the script. Having experience with Agriya's script or group buying script would be a highly preferable. Please do show us the previous work for reference too. Features Needed: 1. Currently, Agriya's script allow administrator to add multiple address to the company. We need to add a feature that allow the user to choose the redemption address of the coupon * Since the address are already there, we just need to add a drop-down list for user to choose the address. Then also print that address at the * require database field adding, displaying the field in the details, showing the redemption address on the coupon generated by the script 2. Currently, the script already allow "multiple deals". For example, user can choose whether to buy "red", "yellow" or "green" iPhone case. But agriya's script do only allow choosing one "type" of product per transaction. We need to add all the "multiple deals" (sub deals) in the "purchasing" page so user can choose - allow this: 1 x red and 2 x yellow and 10 x green iPhone case, for example. - expected result: + calculating the total amount interactively (which is already done) + generate 3 different coupons for the customer. (e.g. one coupon for red color, one for yellow and one for green) + showing the amount of items in the coupon (e.g. add a "amount" field in the coupon, "Amount: 10" for the green one) 3. Adding a "shipping" option during purchase. Just need to add an option for the user to choose. Say if the user choose "shipping" for the redemption method. We will add a "shipping cost" in the purchase menu. A address collection form is also needed to be shown and recorded for the deal. *** all the above features required to support: - front end for customer (purchasing, getting the coupon) - back-end for administrator to select enable/disable the function for each deal - displaying correctly in the deal information page (e.g. just displaying a few more column for the entries) We require good quality code so to make sure the changes with not break anything the site and for easy maintenance. You can access GroupDeal's demo via the link: [login to view URL] We are using the most update version of the script. We know a site that using the same script with exactly feature implemented. Will send through private message about that.