Develop ERP module for prestashop

We need an integration between our ERP-module and Prestashop. The following features is required: Two-way real time synchronization ERP-PrestaShop: 1. Products with attributes and meta data. 2. Stock. Option to choose if PrestaShop or ERP should be master. 3. Clients. 4. Client groups with option to give rebate to clients or client groups. 5. New orders made in PrestaShop, but also new orders made in the ERP-system. 6. Changes made to orders, or order cancellation should be synchronized. 7. There should be an options page in back-office where you can turn on-off options. 8. There should be some kind of offline solution in case ERP system goes offline. PrestaShop should be able to process orders and try to synchronize until ERP system is back online. There may be other things as well. Maybe you see some obvious things that I have not thought of. We will read serious bids carefully. Please make suggestions and say how much this extras would cost. Please link to or explain similar modules you have developed before. We need someone that can deliver good stable code standard. Please tell us if you are certified PrestaShop developer or not. If this project works out good we would need 2-3 other similar integration modules, so please also tell us your hour rate so we know what to expect if we want you to do more work. We may also need some template design/development.