Porterboy, the question to ask yourself is: where would you go next? Because you ain't gonna spend your career in CX, I can guarantee that.
Think POS18 is bad? Wait for the next one.
My advice is, try to go to your career airline earlier than later. If you need to come to CX for the rating, do it. But is a 747 rating useful nowadays?
As for lessonlearnt, yes, the training ban is slowing down our careers progression. But the decision to go with 2 SOs on long haul flights is having a much bigger impact on an SO career progression.