If there DOES have to be a compromise, however undeserved.........
How about giving all the strikers exactly what they want – if, indeed, they know what that is? Give staff travel back with original date of joining. However, give the rest of the company (those that backed BA) a new staff travel priority code that overrides the strikers’ travel seniority. Therefore they will always have a lower priority than those who backed BA and will be placed at the back of the queue.
That way they can’t say they have ‘lost’ ST, or their seniority date. But it ‘rewards’ the rest of us who care about and have supported the company we work for.