Adding such a feature should be fairly easy as the terminal plugin supports tab completion http://terminal.jcubic.pl/api_reference.php
Here are all the possible options

• Hitting tab once will try to complete the current command by looking at the available variables int the current Groovy script context
• Hitting tab twice will show all the available options, if any
• To enable basic method name completion, if available, type . (dot) and hit tab