We have addressed this issue by adding a self-serve image feature.
See
juju metadata add-image juju metadata list-images juju metadata delete-image
eg in AWS, once you have subscribed to Centos(7) images, you can add the ami(s) you want to use,
juju metadata add-image --series centos7 <id>.
Then add-machine or deploy with centos7 series will use that supplied ami.
We have addressed this issue by adding a self-serve image feature.
See
juju metadata add-image
juju metadata list-images
juju metadata delete-image
eg in AWS, once you have subscribed to Centos(7) images, you can add the ami(s) you want to use,
juju metadata add-image --series centos7 <id>.
Then add-machine or deploy with centos7 series will use that supplied ami.