Extending Odoo v8 Point of Sale to allow returning products

Hello. I have 2 year experience working on Odoo. I can give you a single module that will add the required functionality. What I understood about the modifications: 1. Returning an item will require Approval from manager. 2. If quantity is 0, the item should not be sold. How I will approach this problem: 1. Manager will get an email whenever there is a request for return 2. Manager will have to approve the return from within his account 3. Only after approval POS will accept the return and add to the quantity of available stock 4. If the quantity is 0, POS user will get an Error if they try to sell an item with quantity 0. I can add a validate order button that user will have to click before taking up the order. What I will need: The names of your Groups and their access rights to write the module accordingly. What I will give you: A single module that you can install on your Odoo with source code and install instructions. If required, I can give support of teamviewer or SSH for the installation. Free 1 year warranty to fix the module in case of ANY bug or side effects. Hope to work together.