I believe they addressed this in their post because one cannot (currently?) `aws ec2 run-instances --volume-id vol-cafebabe`, rather one can only tell AWS what

I believe they addressed this in their post because one cannot (currently?) `aws ec2 run-instances --volume-id vol-cafebabe`, rather one can only tell AWS what volume parameters to use when they create the root device. Your theory may still be sound about using some kind of super bare bones AMI but there will be no such outcome of "hey, friend, use this existing EBS as your root volume, don't create a new one"