OK, you think the company can rely on seconded crew, you do the maths.
30 flights a day with an average of 15 crew - 450 crew or with minimum crew 300 a day! Now say we strike for 3 consecutive days (even Brian Boyd wont be stupid enough just to do one day), to keep the operation going you would need 1000 crew min.
Your view that non members will come to work is just fantasy, they will go sick. The majority of them want more money and will go along with it rather than break a strike.
The only way to get close to a figure of 1000 even relying on that huge army of seconded crew (Cant be more than at the most another 20) the company will be training up office workers to fill crew positions.
Not sure if you a managment or FD, but if you have a feeling for what is going on at the moment you will know they feeling amongst the crew and dont be surprised if this result will revert back to the 90% yes to strike with a high turnout