Hi,
sorry for late reply, it's a weekend and our offices are closed.

Sorry, you need to overwrite this file on each update. Easy Profile extends Joomla user profile, so registration and edit profile pages are the same of Joomla. These pages are not a part of Easy Profile then we use a system plugin to load tabs.js

Complex Alternative:
We load js files with Joomla API, so to load tabs.js we use this function:

JFactory::getDocument()->addScript(JURI::root().'components/com_jsn/assets/js/tabs.js');

You can write system plugin to manipulate Joomla script references. Before compile HEAD section joomla trigger a system event called "onBeforeCompileHead"

so you can write a system plugin with a function like this:

function onBeforeCompileHead()

    {

    	$app = JFactory::getApplication();

		if (!$app->isAdmin()){

        	    $doc = JFactory::getDocument();

		    unset($doc->_scripts[JURI::root().'components/com_jsn/assets/js/tabs.js']);

		    $doc->->addScript(JURI::root().'components/com_jsn/assets/js/custom_tabs.js');

	  	}

    }

NOTE: This code is not tested and not supported, this code is provided only to example purpose.