Speaking as an American FAA Captain. This would never happen here. Airlines in the USA use seniority for all and any upgrades. I remember when I was flying commuters, we hired some 'street captains' to fly the J31. Just because we were growing so fast we needed them yesterday. But they were on the bottom of the seniority list and only flew what their seniority would allow.
We also have pretty strong unions who wouldn't allow anyone to fly as captains unless they were senior enough to hold the position.
I'll give a current example. We are currently taking delivery of a number of EMB170s. They are being flown by nine month captains. But only because very few of the senior guys want to fly them. Our contract wouldn't allow contract captains to fly our aircraft.
Ryanair needs to be unionized. If not you guys will be flying next to anyone the company wants to hire or contract to fly for you.