Even if he gets to 20 homers, he's not worth a 1st round (or even 2nd round) pick.
You must really not like Crawford if you say he's not worth a 2nd-round pick even if he hits 20 homers... are you really saying in a 12-team league for example that there's 24 guys you'd pick before him even if he had 20 homers to go along with everything else that he does? I think you're going a little far in trying to prove your point with that statement.
If Crawford finished 2008 with 20 homers - a line of: .301 20hr 96r 73rbi 46sb, by my calculations (based on every one else's '08 projections) it would make him the 18th most valuable hitter (in addition to the likely guys: Rollins, Utley, Ortiz, Braun, Sizemore, Soriano, Vlad, Beltran) and I have 2 pitchers ranked ahead of him: Santana, Peavy.
That would make him the 20th highest rank person, which would make him a 2nd round pick for less than half the people in a 12 team league. That's also not factoring in positional strength.