Hello Riot :) I had some thoughts on a Nunu Rework. My idea would be to use the Yeti more by being able to mount and dismount it. If you have the Yeti dismount he should have an HP Bar like Tibbers and be able to attack normally.
mount:
Q remains the old one
W should be a roar of the opponent Fear
E the Yeti forms a big ball and can throw it onto a marked area
R remains the old one
dismount:
Q is a dash forward (he curls up)
W is a snow wall that melts like Anivia's W
E remains the same only that she is now a skillshot and the longer she flies the higher the slow and dmg
R is always available and lets the Yeti come to you
He is said to be a jungler who works great with the Yeti in Jungle without Yeti, he has little chance to survive. For the perfect gank he has to dismount and then use the Q to get to the opponent then place the W and maybe use the E for the dmg and slow (call the yeti with R). Mount the Yeti again and then use the W if the opponent is still alive to knock the E behind.
I hope you like the idea.