I would like to have a $TM_BUNDLE_PATH available in a command, that points to the directory in which the current command is stored. For example, $TM_BUNDLE_PATH would point to /Applications/TextMate.app/Contents/SharedSupport/Bundles/HTML.tmbundle for the Refresh Safari command.

This would make it easier to make more complex commands (just let your command execute $TM_BUNDLE_PATH/my_fancy_script.sh) or pack in some extra resources.