Personally I know there are questions on Khawaja, but I also have questions on Smith. Looking at these two against the big 5 in India, New Zealand, England Pakistan and South Africa., Smith has been worse than Khawaja.
India Smith 68 Khawaja 42
New Zealand Smith 5 Khawaja 88
England Smith 38 Khawaja 23
Pakistan Smith 10 Khawaja 18
South Africa Smith 7 Khawaja 18
Against these 5 Smith 128 av 25.6 Khawaja 189 av 37.8 (Khawaja's performance for a ODI average is good. Smith's is not)
Khawaja is not the problem, Smith is, but appears to be flying under the radar. The last time Smith played any cricket was against South Africa where Rabada and Co exposed his flawed technique of walking across the stumps and the extra pace saw him undone scoring 56, 38, 25, 11, 5 and 7 (average 23) I do believe that other sides see this and are aiming a bit more at the stumps and against these top 5 he was out LBW twice. The lay-off has not helped Smith and I think his days of being a flamboyant batsman could possibly be over. And if they are with the Ashes coming up, it is a bit of a worry.
Wade needs to come in possibly for Stoinis or Maxwell. But that is the problem when you only select 4 specialist batsmen in the side, 3 go early like against South Africa, only all-rounders to come, Thank God for Carey.