Yes, you can modify the file requestshared.xml and either add a new custom status to the file or carefully modify the wording or a request after backing up the original file. This file is located under %USM_HOME%\view\webapps\usm\locale and then under the specific locale folder. For English this would be icusen\request.
When you modify requestshared.xml you need to be sure you modify each list to add a new status. There is more than one location in the file.
As should be done when any file is customized, it is recommended that you copy this file to the equivalent location under
%USM_HOME%\filestore\custom\locale\icusen\request (Or whatever your locale path is) and modify the file in the custom folder.
Should the file in the default location be updated by a patch or upgrade, your customized file will take precedence and you will need to make equivalent modifications to the new file.