I've worked on the other side, with a large enterprise that requires ISVs to deploy their solutions within containers (deployed to k8s/rancher etc) in a closed

I've worked on the other side, with a large enterprise that requires ISVs to deploy their solutions within containers (deployed to k8s/rancher etc) in a closed off VNet. The reason for this was a previous ISV's solution that was sending our customers PII data off to another cloud, and we had no way of monitoring or protecting that data. With regards to your issue, have you discussed your product or SLA requirements if it were to run on-prem? With 3000+ stores and no automation, it sounds like you need to have a conversation about appropriate CI/CD patterns. Ideally you should be publishing to a private container registry, and they should be responsible for deploying that container. In our situation, we understood the limitations we were placing our ISVs in, with our infrastructure bounding their reliability. With regards to guarding their IP, we don't specify that we need access within their containers. We provide access to a private container registry, and appropriate compute and network access for their container to run.