Customize preseed.
Customize template.
Add Debian Cloud's get-credentials.

https://github.com/andsens/build-debian-cloud/blob/bbac6d4efb6c3f5283c6edb840e9c5757d9ff558/init.d/ec2-get-credentials
Customize get-credentials.
Create zerofree.
Create build script.
Create test scripts.