I definitely see the DJ angle with his prior ties to McVay and potentially returning to SoCal.
However, there are a couple of things that come to mind with respect to him and you've already mentioned one:
1) IMO, Jackson is sorta like Britt in that he's a one-trick pony in terms of running the post routes. However, Britt has shown some additional flexibility in being able to use his bigger body on slants. Overall, I'm thinking that a resigned Britt comes cheaper and provides more value.
2) Robert Woods is a better all-around WR than either of the two mentioned above. And because of his football IQ, I don't believe that he'd have any problem picking up the offense. Woody would be another player returning to SoCal.
I'm looking more for value at the WR position as I think the big chunk of our FA $ will need to go towards solidifying the OL.