@2unlimited: I know how it works in LOT (of course you fly when they need you to fly and not when you wish) you make a polish company and invoice a company that cooperate with LOT so I believed it worked the same for Wizz Air and Ryan Air in all nations with a law like Poland but maybe they like it more complicated I do not know. But then why make it complicated? But what you do clearly not know is that in Poland (and probably a lot other Eastern European nations) you are legally allowed to work for just one customer as a company. No matter if you are a plumber, doctor, carpenter.... you name it and also as a pilot. The parliament actually considered changing the law but it was scrapped and it remain as it is. Well either way its definitely on topic that people get to know they wont get such a national company deal with Wizz Air as they could expect if its true as you say.
I do again not wish to go off topic but I do really know ECA is an European organization but do you believe being an European organization gives someone power to decide about national laws of EU member states really? Every nation is only bound with the treaties they sign and EU is not forcing anyone to sign any more treaties its actually enough that one nation veto it and its not only Poland who wish to make their own national laws. So as I said it is legal both in Poland and many more nations in Eastern Europe to have only one customer. As for negotiating with customer you just described a negotiation: the customer says: I want it this way on those terms take it or leave it and you as a company decide if you take it or leave it.
PS. If someone is flying for a company for 5-10-20 years then he is probably captain by then with very many relevant flight hours. Then it should not be hard to immediately get another job on the type in an another airline as DEC having the experience. So getting a lower salary (it cost the airline more so they can pay less) and paying 32 % of your salary for 5-10-20 years just to have a slightly less risk of being fired? What about airlines going bankrupt who will refund the 5-10-20 years of paying 32 % (instead of much less than 19% after deduction) and getting a lower salary to those employed pilots? But of course everyone should be free to choose, thats what I am all about freedom of choice instead of a forced scheme by the state.