It's not at all obvious, but I think the best bet is to 'do nothing'. You can't re-arrange this far out and get ORC. You have to wait until you get cancelled on the day and re-arrange it then under IRROPS (irregular operations). It's a pain as you have to live with the uncertainty but I don't think there is a pro-active way to do this.
Maybe the strikes don't happen? Maybe they don't affect your flights? All possible at this stage so anything the airline doesn't do for you automatically would be a volountary change on your part and you would get the TP for what you changed to.