The year end "world-changing" prospect is up for grabs now. To try and sweeten his deal, I was going to offer him a ML contract, then send him to AA. Are there any drawbacks to signing an IFA to a big league deal ? Or should I just stick to offering a minor league deal with ST invite and try to be the higest bidder?

His option years start running immediately if you sign him to a big league deal. If you figure you're going to have the guy in the majors in about 2-3 seasons, that isn't necessary a big deal. If he needs more development time than that, you're shooting yourself in the foot.

Also - you'll tie up a spot on the 40-man roster which otherwise wouldn't be necessary for his first 4 years. If your organization is reasonably deep with prospects, that means there's an extra one who will have to be exposed to the Rule 5 draft each year.

Still, if this kid's really in the superstud class and you're still not top bidder, you might as well make the ML offer. You've said it's "year end", so you're likely to be stuck with a pile of bonus bucks if you don't get him.