If you know there is going to be a 1 day disruption due to atc strikes, with spare aircrafts why not reschedule some of the flights you can't reroute, for the following day. You know there will be a lot of passengers you now have to feed and overnight. And if your loads are consistently around 90% you are not going to reaccommodate them all on other own flights in the near future. You could use the crew that would be at the end of the working part of their 5/4 rosters and move 1 of their working days 1 day out, plus some standbys. If slot restricted just move the times slightly.
Being in the eye of a better educated public, on the watchlist of regulators, and having to stick to the rules at times of cancellations means one have to think in new ways you before didn't want to. Sample, now need to have prearranged rates and agreeements with low price hotels and bus companies at least near your bases, so you can just call and block book at reduced rates. Plus the need for trained on-call extra ticketdesk staff and floorwalkers.
Also need new insights into how much a disruption really cost you since with a get your own food/transport/accommodation and claim back attitude, actual numbers will only be available months down the line and more difficult to pair to a specific event.