^You're probably right about Abraham not being able to play in space since he's a rusher that relies more on strength and technique rather than speed and athleticism. But still, if he's cheap and still effective, they should sign him just to be a 3rd down rushing DE. You can never have too much pass rushing depth.
Not to mention they spent 65% of their snaps in a sub defense with a four man line. Playing OLB in the 3-4 is getting less and less important. Besides, we have Ninkovich and Anderson (if he's re-signed) already playing that position well.