Who is going to protect the back 4?
Ox may have a few good games this season, and including Ramsey and Xhaka, they don't really have much defensive sense.
Monreal and Kos a year older... you don't want any protection in front of them? Ramsey to protect Monreal?
If you have Gibbs to replace Monreal, then you have him and Ramsey going forward more a lot.
From your formation, I don't see a decisive and precision passer (like Ozil) and a creative player (like Santi).
So we rely on Xhaka's inconsistent long passing, or Ox inconsistent dribbling, or Ramsey you-won't-know-when bombing forward to create chances for the forwards?
To have Bellerin, Ox and Theo on one side, none of them can cross the ball decently.
I don't like Giroud to start, but at least he could be the focal point to start an attack.
Can injury-prone Welbeck play as the striker in 4-3-3?
Theo and Lucas/Iwobi are not good crosser/passer (including Welbeck). This would be a huge downgrade if there is no Sanchez, who could carry and protect the ball well, and create scoring chances by himself.
If there is no replacement of Ozil and Sanchez, sorry to say that we are not even a top-4 team.