My picks won't be as in-depth as you guys, it's mostly based on what I read but also who I've seen in matches on my trips to the Netherlands.
I'm going to cheat on my front three, not sticking to the categories that you've put them if that is okay.
GOAL - Steklenburg (always a safe pair of hands when I've seen him, Romero as reserve)
RB - Stam (Jaliens was closest, haven't seen enough of the rest)
RCB - Vlaar (quality, Alderweireld as next best)
LCB - Douglas (surely snapped up from Twente soon? - Vertonghen next in line)
LB - Gio VB
(for the experience, Tiendalli next)
DM - Engelaar (I'm a big fan of his, if not him in this team... Fer)
CM - Afellay (a popular choice
De Zeeuw just edges out Schaars for the reserve)
AM - Perez (done it at some top NL clubs, Maartens closest to him)
RW - Ruiz (seems perverse not to have Suarez in, but he's first reserve or maybe Wijnaldum)
ST - Lens (really impressed me earlier this season, pace to burn, if I'm not allowed to cheat then I'll take El Hamdaoui)
LW - Dembélé (like his talent, Dzudsak next, haven't seen enough of Eriksen or Biseswar)
So I make it Twente 4, Ajax 1 (!), PSV 2, Feyenoord 2, AZ 2
Can't believe I've got no Ajax outfield players, but that's how it's come out.