I think if Arsenal can make a few more suitable signings in the January window they will have more options in different positions in the team and will be able to compete in both competitions without the fear of burning out their key players with the large number and tight schedule of games but I will also advice to focus more on the league where they already have a bigger opportunity to win it than in the Europa league.
Arteta has planned to bring in several young players who are no less talented than the Gunners' core players. Like it or not, Arteta has to bring in several new players in the January transfer window to smooth out his mission of winning two trophies at once this season. as you said, Arsenal will have many options to compete in two competitions at once without having to always rely on their 11 main players continuously. however, Arteta's attention will be more focused on their domestic league.
and as I said in the previous post, Arsenal have crucial games in the second half of the season in the Premier League. the reason, as we know before. often times, Arsenal underperformed after entering the second half of the season. like it or not, Arteta must prepare his troops to continue to appear consistently until the end of this season and add ammunition in the winter transfer window later. the Europa League trophy is the second plan, after progressing smoothly in the domestic league.