If you and RYR accept that they are a seasonal business, and that RYR would prefer crews to take holiday in winter, why not suggest an incentive package. I once flew for a charter airline, very seasonal. Those who gave up summer leave voluntarily received an extra 2 weeks in winter. The company didn't want you then anyway and it was a WIN WIN. You were at home on pay not flying; days off or SBY; so why not be on paid leave. Same cost, but they had you when they needed you in summer. It just needs a little imagination and common sense.