The members of the team without a club were long serving All Whites who were chosen on the basis of loyalty, experience and temperament- that's two players, both who were in the last WC squad.
Certainly Paul could put up his hand- but the best way to do that would be to try to get a gig in a better league. It is also a tough position he is playing in with players in the EPL, Championship, A-league and ASBP who are ahead of him at the moment. The ASBP or the Australian state leagues are taken more notice of here, though there are a lot of NZ players who have done well in the state leagues who haven't come into consideration.
Though there are others such as Fenton, Clapham who have.
Can he play defensive midfielder? This is a position that is open for contention. Though again there are Tuiloma and Paine playing in Europe, though admittedly at youth level in this position.
If he believes he is a capable enough defender both Andrew Durante and Ben Sigmund at the Phoenix are older players- 31 and 32 respectively. If he thinks he could challenge for a place as they age he should get in touch and let Ernie Merrick know. There are though two younger defenders already on the books- the highly competent Michael Boxall and Luke Adams who are 25 and 19 respectively. I suspect though that the A-league is a step above the S-league, which I heard as being on par with the ASBP.