Not paying someone for 12 months, and then not at all if they have left in the meantime, would appear to breach minimum pay legislation, in the UK at least (possibly also in Ireland and other EU countries).
Saying they will not be paid the amount due if they have more than 4 days sick in the intervening 12 months would act as an incentive to wish to work when unwell, which should surely attract the attention of even such a toothless regulator as the Irish CAA.
Interesting BBC take on the situation, at last now questioning the Ryanair official line
http://www.bbc.co.uk/news/business-41319482