Ubercart

I am looking for someone to help me customised the payment feature for Ubercart. The customisation will override any installed payment modules such that the payment will not occured at the shopping cart. Upon checkout, the administrator will confirm the order and modify shipping charges, discounts and taxes. Then the administrator will set the order to pending customer payment. The customer will go into the order history page under his account and then select the payment method. At this point the customer will be directed to made his payment online if Paypal or Credit Card methods are selected. If online payment is completed the status will change and the process is as per normal ubercart. If offline payment like bank transfer is selected the customer will have to make the payment and update the status through the order history page. The administrator will confirm the payment and change the status through the admin screens.