If there's one weakness and it's not even a major one that I've seen in Smith then it's with the in swinger. I saw Umesh Yadav trouble him a bit with it. There are two issues- There's no English bloke that can bowl that 90mph regularly and also Yadav skids on to the bat. Anyhow, the weakness I saw was having a short mid on next to the pitch and bowl fast in swingers at him. The English need to start from just outside off though and then tail in. This does two things- It demands Smith to make sure he has complete control on the flick or to not exaggerate the shuffle which he's very capable of doing now. BUT, he's not as good as he is when he doesn't cover all of off stump and tends to nick off a lot more.
England need to be a bit ballsy. I think a leg slip, short mid on (next to the pitch), a mid wicket and a square leg with this line of attack will be super interesting. It's imperative you leave cover open so that when you bowl the sucker ball for the nick off he looks to bite and not leave the ball. It means Smith is constantly under pressure to be in control. If he misses one ball, he's plumb in front and while he might get 4-5 boundaries away you might just get him out.
If any of you notice, Smith never opens his shoulders enough to look to hit the 4th stump line to mid wicket or square leg. He looks to hit them to mid on or straight. This is why he doesn't get trapped in front all that often. Once you put that short mid on, he will fear getting caught even with 90% control over the shot. It forces him to hit more on side and open his shoulders more which can't go on forever. He will fall over or get trapped sooner rather than later.
I'd try Broad with this tactic. May be even a slower ball as well. Mind you, Broad's been pathetic today.