If Dallas ends up with a top five pick, it would be reaching to draft a DL first. This is a really bad draft for top end defense talent. The only way to get value would be to trade back and draft defense.
There's a paper by Massey and Thaler from back in 2005 that tends to support the idea that the only good use for a high pick to trade it away for more picks. In having the #1 pick a team is paying a premium for a high (first pick) who rarely, if at all, provides a surplus (field performance) better than a low first rounder. They consider the compensation vs surplus to level out in 2nd round, starting with the 10th pick. That is, in their study the, "get what you pay for point".
They conclude......
"We began this study with the strong intuition that teams were putting too high a value on choosing early in the draft. We thought it crazy for the Giants to give up so many picks for the opportunity to move up from the fourth pick to the first one (regardless of which player they chose). But we concede that we did not expect the findings to be as strong as those we report. Rather than a treasure, the right to pick first appears to be a curse. If picks are valued by the surplus they produce, then the first pick in the first round is the worst pick in the round, not the best! In paying a steep price to trade up, teams seem to be getting the sign wrong!
"Indeed, the irony of our results is that the supposed benefit bestowed on the worst team in the league, the right to pick first in the draft, is really not a benefit at all, unless
the team trades it away. The first pick in the draft is the loser’s curse."