Best practice sending container command to register for license

I have an image with an entrypoint script.
I added many functions to my entrypoint script, but the more I use it, it seems like a one time script just to initialize a container and then, you can no longer access its contents, save, docker exec or logging into container.
My entrypoint script allows for; help, install, register.

My question is; What is the best practice for letting users access additional functionality, such as register the software that is running in the container.

They start the image, play with the software and decide they want to try to licensed features.
Is there a best practice to do a docker exec? or would it be best to provide some type of API endpoint?
IS there a way to pass new arguments to the entrypoint if they stop and then start the container, however docker start commands are limited I noticed.
Can a user set environment variables, I can then check for to determine if they want or have registered?
Can the user pass in extra arguments after restart or running container?

Trying not to ask the developers to create an API endpoint in the software to expose, but if that is the best practice i suppose I should ask the developers.

Thank you for your time and expertise.

In my particular case, being a database we use persistent data.
This allows one to run the container with just the basic installation. After some development the user decides to register and use enterprise features, they only need to run the image again with the arguments to register and the persistent mount point is referenced by the application after another run of the container giving the user access to the enterprise features.
Ideally, but because resources are constrained, it would require our engineering team, an authorized API call to register for enterprise features will be implemented in the future…
Thanks for listening.

We went with API calls to the software.