John,
Yes, both in the current and future etm reports you would enter '-c John Smith -b <begin date> -e <end date> as report options'.
While there is nothing to prevent your using '@c' for this purpose, you would be much better off, especially in the future etm, to use '@k SmithJohn' or, better still, '@k SmithJohn:ProjectWhatever'. Then when you group by keyword and then date in reports all the 'SmithJohn' entries would appear together, sorted alphabetically and sub grouped by project and date. The built-in keyword view in the new etm would do almost the same thing automatically (sorted but not grouped by date).
-Dan