OMV targets home users, right? So, this way sounds right to me. The more professional users can install docker first and so they are protected against removing all containers by removing the plugin.
For me, the possibility to activate/disable the docker demon within the GUI would be nice.
In the moment no container is running and I don't need docker running, but will keep my containers. Disabling docker by using the CLI to looking for the settings the plugin made and change them is very sophisticated to an home user.