Ryanair have huge cash reserves, but I doubt that MOL will allow any of that to be spent keeping crews on the pay roll if he doesn't have to. Hence the "option" of unpaid leave that is on offer.
But, between now and 2012 Ryanair have another 100 or so B738's arriving and under their model they need 6.7 crews per aircraft to keep them running (Eddie Wilson's figures) and shedding 600 crew just does not add up.
Perhaps 600 crew in total (Flight Deck and CC) is the number being looked at for "unpaid leave" over the winter period when Ryanair won't be as busy. They demand total flexibility from their staff (i.e if the company makes money then the staff can have some too) and maybe this is the move from MOL and his henchman to seek further "flexibility" from an already stretched (financially speaking) workforce.