I think Morrow was truly one of the most interesting characters in Ninjago and would like for him to come back. I must also add season 5 and season 4 were my 2 favorite seasons which adds to why I would want him to come back to the new seasons of Ninjago.
On his almost entire TV appearence, Morro, The first student of Master Wu, Was shown as an antagonist ghost from cursed realm. He possesed Lloyd and took the realm crystal to release the preeminent in Ninjago. His plan was working good until Nya found her true potential and the entire cursed realm drowned. Morro seemed to redeem himself and accept his fate when master wu tried to save him. He gave to his old teacher the realm crystal, To save Lloyd, And returned where he belongs on the departed realm.
Also he had a small role in the day of the departed when instead of fight with master Wu, He helped the ninjas by telling about Yang's plan.
He was too short on screen and most of the time inhabited in Lloyd body, But i think he will made a great job as good guy too.