Give Kalistas ult the Thresh Lantern treatment
What do I mean by this? well if you have any hard CC on you, you CANNOT grab the lantern, so make the Kalista ult have the same treatment
"But then her ult will be useless against CC heavy teams/if her and her oathsworn get caught" Thats the point, thats the reward for chaining your CC, or the Punishment for overextending you're rewarded with a free kill, instead what currently happens is the support gets pulled in having after taking the hard CC and then comes back in with the second use of the ult or the Support plays sacrificial lamb for Kalista to escape a bit.....then gets pulled to safety despite that fact Tahm has you in his stomach.
It just seems rather stupid when Thresh and Kalista have a near identical kill (Just swap roles and swap shield for Maplhite ult) but one is stopped by hard CC and the other is CC immune