@theinvisibleworm:
I think that Smoker could match Ao Kiji. Though we have no real gauge as they both owned Luffy, but we have no idea as to whether or not Smoker could get Luffy into a submission like that with Luffy's improvement over time, and we know Ao Kiji could (except with regards to gear second, which will give luffy at least a good chance at matching their hand to hand skills, but the logias are a different story entirely).
What came into my mind was that Smoker maybe isn't that strong after all… He can evade attacks and use his smoke-body grab people and to confuse them for a moment. But that's about it: Unlike the other logia fruits his attacks aren't boosted by his element in the sense that they're deadly.
Ace and Eneru can burn people to crisp, Crocodile can cut and dry out people and Ao Kiji - who's powers have been developed to the most extreme extent that we've seen yet - can freeze enemies until they're as fragile as glass. But "smoke" isn't deadly at all, unless you get some Smoke Poisoning or run out of oxygen - which didn't happen in the manga.
And remember how Luffy did that Gomu-Gomu-Balloon Attack on Smoker and escaped from his grasp? Smoke has a very low density, so it is possible that persons who are physically strong can free themselves easily, without being affected. Pure speculation, of course XD But I really doubt that Smoker is stronger than Ao Kiji. It seems wrong.
And he most likely wasn't in Ohara either, because the part of the »Highly ranked Marine-Person who sees the cruelty of the Marine and begins to have doubts about the Marine's "Justice"« is occupied by Saul already. Smoker would be out of place.