I was considering writing something similar: a "semi-mocked" implementation of all of AWS, getting you most of what you get from running OpenStack but from one static binary running in userland and with no persistence.
My use-case for it was that I'd write it all in Erlang, and then each public port on a mocked EC2 instance would have a single Erlang process hooked up to it to respond to messages coming to that instance-IP:port. So you could set up something that looked like a thousand-node distributed VPC, from the perspective of an AWS client talking to the API, and it would all sit in a couple MB of RAM and near-zero CPU.
My use-case for it was that I'd write it all in Erlang, and then each public port on a mocked EC2 instance would have a single Erlang process hooked up to it to respond to messages coming to that instance-IP:port. So you could set up something that looked like a thousand-node distributed VPC, from the perspective of an AWS client talking to the API, and it would all sit in a couple MB of RAM and near-zero CPU.