The feature request is in the title already but ill explain it anyway, Ghast should start fighting back with the wither storm after the ghast either.

1. Notices the wither storm and notices the mobs running away
   or
2. Ghast gets stuck in the tractor beam and fights back to escape.
   I Tested it out before I made this feature request to see if they do fight back on the latest update and no they didn't fight back.
   And if you think " But Ghast don't spawn in the overworld, and the wither storm cant go in the nether!!! " Spawning ghast in the overworld is a option to.

The Wither Storm doesn't target ghast

The Wither Storm doesn't target ghasts and there wouldn't be really any scenarios where ghasts would encounter the Wither Storm to attack. Yes you could spawn them but I don't think this feature is entirely necessary, sorry.