I should reiterate, Chris Clemons is not an athletic freak. Raheem Brock ran a forty time that was just barely faster than what Dontari Poe had. Bruce Irvin IS fast, but still appears incapable of being a true LEO due to other shortcomings.
Sadly, there just isn't an "ideal" LEO in this draft that will reach our pick. Even Clemons isn't truly one. I don't think Okafor is going to be a super star, but I think he could give us maybe 75%-90% of what Clemons does. If you watch him closely, you'll see that Texas kept alternating him from a 5-tech role to a 9-tech role during games. As a 5-tech he's just okay, but as a 9-tech he improves dramatically and is constantly creating pressure.
I kind of hope Seattle goes TE/WR at #25 because that's where I think the value is, but if they draft DL there instead (assuming Red Bryant isn't going anywhere), I think Okafor could work out very nicely as a pure LEO.
My preference would be to sign Cliff Avril in FA, but if Seattle ends up having to address the D-line in the draft early, and a colossal trade up is off the table (likely), I think Okafor is one of the best realistic options at #25. I would much rather take a poor man's Chris Clemons over a Jason Jones clone (Ansah as a 3-tech), or an Alan Branch type (Kawann Short, Sharrif Floyd). Seattle can survive another season of Branch + Jones if it came to that. But they can't survive a season that banks on Irvin playing the LEO or Clemons playing the LEO at half capacity. LEO has to be a huge consideration. I think guys like Okafor and Simon are worth long looks as LEO candidates. Though Simon is the better pass rusher, I would prefer Okafor just because he does not come with any exploitable features like Simon does.