Any of the alumni could return. Shield, Wyatts, Dallas, Rusev, Big E, Cesaro, Paige, Emma, Kruger, or Ascension.
Send Fandango, Axel (seriously, not two appearances), Xavier Woods, Darren Young, Slater, or Ryder.
Then of course we have former WWE guys like Kendrick or Rhyno, there are dozens...