From what I hear from friends working with Ryanair a union will be very much necessary. The advertised promisses like share options, fixed days off, great pay etc...all a bit like big mouthed words.
No captain nor any type rated first officer can join Ryanair, all have to accept an agency contract. These contracts are subject to "take-it-or leave" Ryanair changes.
There is no minimum guaranteed....think about the guys and girls who just fly 1 or 2 days at present. And...ask them if anyone can remember when the salary was last paid on time...