It seems that you want to make your root volume as small as possible, and use it to only attach a pre-warmed pool of EBS volumes at launch time that contain the

It seems that you want to make your root volume as small as possible, and use it to only attach a pre-warmed pool of EBS volumes at launch time that contain the actual config/data you need? You can launch a stripped down distribution with what, a 200mb disk? Then attach the “useful” EBS volume, and “do stuff” with that - launch a container, or whatever.