Terrible idea.
Basically you're
paying someone to fly a jet for which they should be
paying you to fly.
Besides, the amount of experience you get in blocks of 250 or 500 really isn't substantial enough to make a difference. I really didn't develop any real "yeah, I'll take the visual on the runway without the ILS or VASI" comfort with the MD-88/90 until about 800 to 900 hours of experience
If I'm a regional airline looking for a pilot, and an applicant has 2000 hours and 500 "EagleJet" hours in a A320, big deal -- we don't fly the A320.
Also, airlines want to see experience in your logbook in which a hiring manager thought highly enough and assumed risk to hire, train, and then appropriately compensate you for your services.
Besides, my personal advice would be to save the money, build flight time the traditional (and logical) method and save the money for a 737 type rating to apply for Southwest Airlines (that's a world of difference).
Actually, hell, the best bet if you had $50K just sitting around would be to throw it into a good no load mutual fund!
And for the record, I haven't run into anyone at Delta or Skyway that took part in an "FO Program". It doesn't mean someone's not lurking on the website that has (save the 'heated' email, thank you).