The problem with just adding more containers is that you still need to have the server resources available. Even managed Kubernetes clusters offered by private cloud providers still require the underlying VM capacity to be present.
At the moment the best way to scale your platform is to provision another VM or bare metal server and migrate some of your workload to that server - we make this very easy to do through the panel. If you have a particular busy website you can move it to its own VM with no need for the customer to change their control panel and no impact on your licence cost.
It's delayed a little but when we release the "hard resource limits" feature you will be able to do this and almost eliminate "noisy neighbour" issues.