Arsenal's main target is not the Champions League but the Domestic League, winning the Champions League is a bonus for Arsenal, but Arsenal's game must remain consistent in the Champions League, even though there are many choices that Arsenal will take next season, that doesn't mean they are unable to compete, Arteta must focus with stamina and mentality that will be built next season.
Arsenal have experienced tremendous improvement in recent seasons in the Premier League, but for the Champions League of course we can't expect much of them to be able to compete with other strong teams, at the moment of course we can't say if they have to focus on one trophy because indeed if they can go through both competitions why not?
The English Premier League is not as competitive as the Champions League, so indeed to be able to compete in both competitions, of course, Arsenal must have a squad depth that is quite qualified so that they can rotate the team well next season.
Arteta should be able to make a few changes and also evaluate his current team to find out the weaknesses and also the causes of their failure this season, Arsenal best achievement in the Champions League was the final in 2006, so I think to be able to become a coach that will indeed be remembered by Arsenal fans all the time then Arteta must be able to get the Champions League trophy during his coaching, So that way he will be considered one of Arsenal legendary coaches in the future.