If he failed a checkride he CAN apply to southwest but they probably won't hire him. There's a fair chance that if the hiring wave that everyone says is coming actually comes that you may not need PIC. If that's the case and lets say there is a CHQ FO and a Gojet captain, it's likely that Gojet colors the resume in a negative light. So the CHQ FO gets hired. If you make the jump now and get stuck at Gojet because of some perceived negativity about Gojet, how will you feel? What if the guys that stay at CHQ get fast upgrades and move on and you can't because you've got the stain of Gojet on your resume.

I can't see the future. Maybe no hiring board will ever care. It's your career, gamble however you like.

Just be aware the grass is always greener someplace else...