wenger seems to still be tinkering with how he wants to set up, depending on who is fit/available, but i think his preference, given the last few months, is deeper midfielder (call it a DM if you want), box to box midfielder, and central attacking mid.
right now, we have 3 mids suited for the attacking role: cazorla, ozil, rosicky
we have these as box to box options: ramsey, wilshere, chamberlain
for the DM role, we have: coqeulin, flamini, arteta, and the new kid
looking at what we have, id say if we're going to spend big, it should be on the DM/deeper mid, and we should be looking to buy someone like matic/schneiderlin who is already playing in that role and established in that role. pogba is a box to box midfielder, we already have sufficient depth there. is he better than ramsey and wilshere? well yes, but the difference between pogba and ramsey is smaller than the difference between a world class DM and flamini.
looking at the composition of our squad, going into next season the two areas where we are short of numbers and could use big upgrades are: LW, DM, GK, LB, and possibly CB. i think its extremely unlikely that we'll buy a #9/ST type, because wenger loves giroud and we also have welbeck now. we lack a world class left wing option. we lack a world class DM. we have depth pretty much everywhere else. if you're not a mertesacker fan, and gabriel isnt enough, then maybe we spend a big sum on a commanding CB, but i cant see that. we now have: bfg/kos and gabriel/chambers as our CB pairings, and seeing as we went into this year with 2 senior CBs, i cant see going into next season with 5.
if we're wishlisting, i'd love to see us buy schneiderlin and then the best LW and LB we can get for the money.