This could actually be pretty interesting, it would definitely reward predicting an enemy ult and checking their ult timers, and it'd be pretty fun to catch an enemy during channeling, the only issue is this would be doubly effective against characters such as Warden or Doorman, so you'd probably have to make a distinction between item/ability channeling and ult channeling, so that the item can cancel channelable ults but takes the higher cooldown for it.