Rather than deploying with the root disk as ephemeral storage, modify the instance creation so that instances are deployed with a new volume as their root disk.
This has two advantages:
Root disks count towards the tenancy quota.
The user can pick any size for the root disk that they want.
Rather than deploying with the root disk as ephemeral storage, modify the instance creation so that instances are deployed with a new volume as their root disk.
This has two advantages:
Sizes would just be used for CPU/RAM.