Midfield
Mesut Ozil (Right Central Midfielder)
Ozil dramatically signed a contract extension to remain with Arsenal when for most of January it appeared like he would depart alongside Sanchez; that he chose to stay is as equally important as any new signing. At his true best, Ozil is still one of the finest playmakers in the world.
While his overall performances may have dipped this season, his stats haven't as he is still laying on a good amount of chances for his teammates; players like Aubameyang and Mkhitaryan should be salivating at the thought of being supplied by Ozil.
While he usually has operated further forward for Wenger, a drop back into a midfield three isn't out of the question: consider the great success a similar player like David Silva has had moving there for Pep Guardiola at Manchester City.
It wouldn't necessarily mean more defensive duties for Ozil but would give him more space to pick up the ball from his defenders and try and locate his front three with his passing range. Ozil is a left-footer who loves to drift from right to left, so playing on the right of the midfield three would allow him to make diagonal runs across the pitch in this manner.
Mohamed Elneny (Central Defensive Midfielder)
A player who often goes unnoticed, Elneny would provide the solid defensive platform so vital to allow the flair players around him to express themselves freely. Wenger has gone with a midfield without a proper defensive option in the past and suffered because of it. Elneny has perhaps been under-appreciated in his time at Arsenal so far but it's in the same way that Makelele was treated similarly at both Chelsea and Real Madrid.
When one does the dirty work for the team they can't expect to receive the acclaim of the attacking talent. The Egyptian international is a decent ball-carrier, with a good passing range, but most importantly he will offer protection for his defence and Mesut Ozil beside him. With so much attacking talent for Wenger to fit into his starting XI, it's important not to forget the need for strong defensive quality.
Jack Wilshere (Left Central Midfielder)
A popular figure with the fans, Wilshere returned to Arsenal from his somewhat disappointing season-long loan at Bournemouth last season and has looked far sharper and stronger. He hasn't featured nearly as much as he should have in EPL games so far, with Wenger restricting him to cup competitions mostly, but a large section of the support have been clamouring for his inclusion.
On top form, Wilshere is a terrific blend of ferocity and skill, equally happy being in possession and harassing opposition midfielders. His performances have merited more of a chance in the league and Wilshere's presence would provide further defensive shield alongside Mohamed Elneny.
As a left-footer, Wilshere would also provide a nice balance to compensate for having a right-footer in Lacazette playing out wide on the left-hand side of the pitch. Aaron Ramsey hasn't necessarily performed badly this season so far but Wilshere just offers that bit of aggression and bite that Arsenal needs right now.