I think Arsenal doesn't have to make a major overhaul to become champions because they already have a pretty solid squad and a good coach. At most, they only need to sign a few players who are really needed and don't have to make changes on a large scale. Arsenal's real problem is that they still don't have the winning mentality that Man City and Real Madrid currently have, and I think if on several occasions they can reach the final, it will form that necessary mentality on its own.
They need three experienced players to help them realize the club's success and achieve trophies, the players they have are indeed good but lack mentality. There is no need to make major changes because the squad that Arsenal has is already good, they just need to find some experienced players to make their mentality better. Mentality will be formed when they have players who are experienced enough in dealing with pressure.
It will take time for Arsenal to achieve what Man City has achieved and they will get that experience if they are able to maintain consistency in playing. In the Champions League, experience and mentality are very much needed because the competition is much tighter with several representatives from the existing leagues. Arteta must build this squad to be more ready to deal with pressure and they must try to find the right momentum.