Fun idea to change janna to be a bit more... fun
Janna to me is a boring support, she is full utility but other than an occasional shield/well placed tornado, she doesnt match up with other supports Imo.
Simple change i think would make her fun, and open up some amazing plays/scenarios for league.
Make her tornadoes carry momentum, but still knock up.
Picture a baron kill, you're in the pit trying to finish off baron, and just as Nashor bites the dust, the enemy team closes in on the pit opening. No flashes up, It looks like sure death and yet another infamous baron throw. Then your support janna places a tornado towards the back wall, Your entire team runs towards the wall, and the tornado knocks up everyone, carrying the momentum of movementspeed as well as dashes, up and over the wall to a safe retreat. Of course to balance this, a lucian dashes at the perfect time and also uses jannas tornado to jump the wall, securing a 1 v 5 penta.
I just think it'd be a fun change to give her more reasonable escape. Enemies could use it to their advantage, but going against the tornado obviously would provide a slow cuz physics.