You have to be joking!
I suppose saying No to Cathay right now as a keen GA pilot looking to break into the majors is going to do wonders for your career! I think not. If you say no to Cathay now, they won't be asking you again.
For many, not all, Cathay may be many pilots only chance of breaking into the majors.
But saying no to a command upgrade for a major airline, which is the ultimate goal for any pilot, may ruin the rest of your career and make all those years of hard work wasted.
OK, How about Saying no to a SO job for a major airline, which is the ultimate goal for any GA pilot, may ruin the rest of your career and make all those years of hard work wasted!