did mustang bloke say he'd paid for his rating? I may have missed that bit. I know quite a few people who have been put on ratings they have never used and then been made redundant or the company has folded.
Mustang thingy, ignore the doom mongers, just apply to everyone who operates a 604 and see what happens. Lots of jet people are quick to dismiss turboprop time but thats because they are morons - most turboprops are significantly more demanding if things go wrong than a jet and if nothing goes wrong they are both much easier than having a proper job so unless you are applying to idiots they will understand that you have put in some decent flying. If you paid for your rating yourself I would suggest that you have made a significant an very likely fruitless gamble but hey, its your cash. I have, coincidentally, got this amazing business opportunity for you if you have any left to "invest"