Oracle Project Billing - Complex Billing Terms and Invoicing Maintenance

We have some standard billing agreements for one of our service client who provide consulting services. Most of times, these agreement specify a total amount but payment terms are based on as below:-

a) Future Date Wise Schedule  with or without conditons

b) Milestone based payment where dates are not known like % Completion etc

In order to make it more specific for the community discussion, we have generalized the above scenario through following example :-

Client X has say entered into an agreement with customer A for execution of Software Developmen project. Here are the sample terms of the agreement for Billing purpose :-