You're right of course. Habent included joel as he's not the same 'level' as the others...could have him as reserve of course.
Yes, some of the players can play multiple positions such as Barkley/ Cleverley/Mirallas and also McCarthy etc so we wouldnt need 2 AMs for example...
It does show however that we need:
Keeper
Winger
Playmaker
Forward
And logically a centre back whilst the kids come through...however the other kids may fill the bench as well for some of the other roles...who knows.
If we signed Austin, playmaker and a centre back then next summer lost a LOT of players (5 contracts expire) our pot next summer could go entirely on a winger and a keeper and we would have a heck of a lot of TV money to get real quality in and alot of spare wages not only for new players but also to keep existing ones happy.
There's value looking at it this way, but it's very rigid. Why do we need two starting XIs composed of 100% long term players? Many of our players are flexible, anyway. Kev and Ross can effectively play AM, for instance. You've also forgotten Joel is a young goalkeeper and can be considered "long term."