The danger of making such a trade is that you don't know what value will be available at #20 when you make it. We may project that a quality DE or DT will be there, but there are 14 picks between #5 and #20. What if there is a run on D-linemen (or TE's, DB's, etc.)? Besides, according to the "Trade Value chart" (
http://www.nfldraftview.com/tvchart.html), we'd be getting the short end of such a deal. Unless there was also a swap of players/salaries, this deal isn't good enough.