Right now the DL is DE-heavy, and 1-technique bereft. Beyond D-Law and Russell and whatever Gregory is allowed to do, Crawford and Irving are both very much DEs in size, speed and motor. Getting both a playmaking starter and competitive depth at 1-technique can allow more interchangeable packages with some of the size and speed at DE and 3-technique. Right now Crawford is almost too pigeonholed at that pivotal 3-technique that Dallas can't afford not to have him there or to shift him around.
Truly, if an offense is game planning against a DL player, it's Tyrone Crawford and not Hayden. Should find someone who can set Crawford free by getting greater or equal blockers attention to what Crawford gets now.
Whether by FA or draft, it's silly to keep adding DEs when the real issue is the interior.