That group of players you've listed is a diverse bunch and in my opinion should never be competing for the same spots in the 22. I spent some time this morning reading over some stats and I noticed a trend of sorts. You can classify players as uncontested or contested by the ratio of those possession types. In general players who have a ratio greater than 2:1 are outside uncontested types, and those below your inside contested players. The absolute elite outside players tend to go at a ratio above 3 and the elite inside clearance machines, Dangerfield, JPK, Fyfe etc, at or below 1. Those players you mentioned over their careers go at:
Aish: 1.7, Greenwood: 1.34, Wells: 1.83, Phillips: 3.08, Smith: 3.16, WHE: 1.81, Blair: 1.05
Right away we should take Phillips and Smith out of any discussions about whether Aish plays or not as they clearly play a very different style of game. Next WHE stats are a little meaningless as a midfielder as he has spent most his time forward and the same goes for Blair. Although on Blair that is not a good ratio, he does not win enough of the ball to justify such a low percentage of uncontested possession.
That leaves just Greenwood and Wells left to compete with Aish for a spot. I agree with you that Wells is clearly ahead of Aish but I believe Aish is a better option than Greenwood. Greenwood averages 18 disposals a game, 10up and 8cp. That's a good balance but given his poor disposal that is more like 5up and 8cp. That suddenly does not look so hot for a senior player. Aish on the other hand is young and if we ignore his time at Brisbane his ratio changes to 1.4 at an average of 15 disposals, 9up and 6cp. Given Aish's disposal that is more like 6up and 6cp for an average of 12, one less than Greenwood. Given Aish has much greater scope for improvement than Greenwood and his game on the weekend was more reminiscent of his finish to last season, if it comes down to Aish vs Greenwood for the last spot in round 1 I would prefer to see Aish get the nod.
Specifically on Aish I'm a little concerned that in Buckleys post game press conference he mentioned Aish when listing players who can play a role on the wing to allow Sidebottom to play forward. Looking at these stats he is unlikely to rack up enough possessions on the wing to be effective in a true outside role.
Finally in case anyone wants to accuse me of cherry picking Aish's 2016 stats while using Greenwood's career totals to suit my argument, in regards to the stats I've used, Greenwood's 21 games in 2016 yielded results spot on his career average.