Bundling of Projects to support

Hi,

My client is interested in gouping projects into an Arrangement and billing at the Arrangement level under one invoice.  I fully understand that projects only support one invoice per project and agreement combination.  I also understand that revenue and billing cannot be created from a program - it has to be at a project level only.  What I'm looking for is some thoughts on approach to support grouping ofr projects into a master Arrangement and recognizing revenue and billing at the Arrangement level even though we are collecting costs at the individual project level.  I am aware of utilizing Interproject