There should be a button to upload a CSV file with a list of your customers and have them all be created with default options.

Even better would be to allow multiple columns in the CSV where you could specify subscription, security level/template and message template options to further reduce setup time. There would be a CSV template file you could download with examples of how these all need to be formatted to minimize issues with the import. If the import fails it should spit out the lines that failed and why so the user can correct them and try again.

Another option would be to have the CSV import be the first step of an import wizard. After the names were imported then you would be able to use batch selection methods to apply the above settings to all the customers and manually change any you would like. Then at the end of the wizard the customers are finally created.