Hughes has been amassing a mountain of runs at Shield level, but he always did and then was more often than not found wanting in technique at test level. Has his technique improved to the point that he could now be relied on in the test team? Given that uncertainty, I'd be happy to see Doolan given his chance to show what he has.
I would be very unhappy if Doolan was given his chance to show what he has. Simply because based on this year's performances and an FC average of around 37, I don't see any indication that he has that much.
The accepted level of a decent batsman is an average of 40, so really any player who has not amassed enough runs at a consistency over their career to achieve that we should disregard.
In the untried department, that leaves Chris Lynn with a good average of around 43, then Nic Maddinson and Joe Burns a little over 40. \
Then in the experienced department we have North who is averaging something ridiculous like 80 for the season and low 40's in his career as well as Voges, White and Cowan over 40.
If anybody is going to come in, they should come from these players. To disregard them and pick a Doolan or Silk would be to expect a player to suddenly improve performances at a higher level, which is a little unrealistic.
My vote would go to either Lynn, Maddinson or North to come in as a 6. IF it's Sydney I'd go with the younger 2. If it's SA I'd bring North back.