What I've seen here and there (and is not necessarily well-documented) is that Smoker's fruit works more with the "stable" type of gas. If you've seen HXH and watched Morel's powers you could understand the situation much better. Ceasar is essentially toxins transmitted via air, some flammable, some poisonous. The main reason he could cut out Oxygen, was his body reacting with it. Now, Smoker's body is a mix of carbon gases, like CO2, methane etc which means he can form something from "physical smoke" and also has properties of "jet" and "steam", which gives him enough potential for the future.
Now, while Ceasar can use various instruments around to emit pressurized gas or fire it, Smoker can work around with his smoke to form illusions, use it as propelled gas (like he did in Marineford to propel himself into the air) or simply increase his volume and fighting power (similar to Akainu's DAI FUCKING FUNKA)
That's all I have for now. It's a shame he have seen nothing from Smoker's abilities. I am almost certain that next time we see him, he will have endured harsh training and awoken his DF - long before any of the main cast (as he needs to gain a huge advantage over Luffy again, fast)