Add features to existing Symfony2 project - repost

I have an existing billing system written in Symfony2 PHP by another developer. The system works well but I need some new functionality added to it, and since my existing developer is working on some other functionality, I'm looking for a second developer. You can assume the existing system is coded to a high standard and well structured. I need the following changes made: 1. Currently the system supports payment by Paypal and offline payments. I want to expand this to include payment by Amazon, Google Checkout, 2Checkout and Stripe. 2. A new "reports" page should be added, allowing the admin to gather graphical and tabular data about gateway performance, client performance, 1 year financial statement, monthly statement etc 3. Currently the system only supports a single tax band. This should be expanded to allow for any number of tax bands. 4. Currently the system only supports a single currency. This should be expanded to allow for multiple currencies throughout.