Wenger as Director of Football will likely impact negatively on Arsenal for years, as an ambassdor and talking stupid people into signing for the club when there are better alternatives... maybe, he used to be able to do it, but then again he failed to do that with Mata, and Ronaldo, and multiple other players, but did manage to persuade the likes of Chamakh to join Arsenal on a huge wage that seemingly on one else was offering.
Ultimately if he stays involved in the club on any serious level, I think he'll be helping coach kids, helping pick youngsters for the youth squad, poo poo'ing deals, ie new manager wants to cut half the team buy 2-3 stars on 150k a week and everyone else on significantly less, I can see Wenger sticking his oar in with the board and saying we can't do that, and putting in his idea's for who we should buy and the like.
Wenger though, has lost all ability to spot a player now, he has no objectivity, and coaching, I can't remember the last player who joined Arsenal and improved rather than regressed, some significantly. A player like Cesc or Wilshire are just those once in every while players who get football, they'd become as good playing at Barca, or Grimsby, Cesc joined as an incredibly talented player he didn't improve drastically in 3 months then was suddenly exceptional.
So frankly, I don't want him to have anything to do with shaping who we go after, youth teams, what players we keep or how we organise the team, because the entire reason we aren't competitive is down to those factors.
Wenger of pre unbeaten run ending era, I'd have as a director of football in a heart beat, he could spot a good player and wouldn't tolerate someone as crap as Denilson, pushed for improvement in the squad every year and pushed for a better kind of football.