Anyone can but they didn't? Smoker was involved in two warlord incidents. Now there is an ex warlord crew who are a somewhat major force. Dorry and Broggy went from not doing anything in the story for like 20 years to being some of Luffys most important allies,and literally fighting off the Gorosei when the giants became important in the story. Why wouldn't smoker be the same when it comes time for the SH vs marines?
Sure, if we're talking about things he
could do, then Smoker
could still be important. But so far he's been useless. His presence after Alabasta is negligible.
You know why I can say that?
Smoker was involved with Croc's conspiracy in Alabasta. Yet the Shichibukai still stood.
Smoker saw Law do weird shit in PH. Yet the Shichibukai still stood.
Smoker was assaulted by Doffy in PH. Yet the Shichibukai still stood.
Meanwhile, Fuji came in, witnessed Doffy's DR takeover, spoke against it. And the Shichibukai are no longer.
That's a man of importance.
You can argue that the Shichibukai system couldn't be dissolved before DR for plot needs, and I'd agree with you. But Oda still had no reason to use Fuji for its cancelation, when that had been Smoker's sideplot throughout pre-ts.
So far, Smoker has been a glorified babysitter for the giants kids of PH, and even that lead to absolutely nothing.
Anything Smoker does, there are at least ten other Marines who could do it better. He's useless. You'd think Oda could implement him within Sword, yet he preferred to introduce new characters like golem swag dude rather than show both Coby and Smoker alongside Garp.
Whatever Oda has in mind for Smoker, it's too little too late.