This proposal makes a case to evolve CloudStack's architecture past 4.0's monolithic management architecture. I don't have time to pull up a full text based. So I've attached the powerpoint here: CloudStack Evolution Proposal. The powerpoint also makes references to Kelven's work to introduce more standard libraries into CloudStack and Edison's work to further break apart CloudStack's storage piece. Edison's proposal can be found here.
I will come back to this page to make it a more formal wiki.