In this season Arsenal is doing amazing job, and we can expect improvement in coming weeks but can they keep this momentum, and we will be able to watch them as winner of the two titles because they are capable of having amazing stuff and new player's entry can bring more success with good and strong competition.
As Arsenal have started the season and continued their form, they are undoubtedly the frontrunners to win the title this season. Arsenal is financially sound. I think they will try their best to win the title this season. And if necessary, they will spend money to add new talented players to the squad. Arsenal is still 5 points ahead of Manchester City. They will definitely want to maintain this gap.
I would guess that they can add any new players they want if we are talking about just financially, but that doesn't mean that it will help them all that much quickly. It is not a one season thing where you get someone in the middle of the season and suddenly become champions. Even Liverpool can't do that and they already have a good roster.
It is more about the fact that we are not seeing anyone really do anything big in the end with just one big name coming at the half of the season. However, they could give it a try, like get the player and give them time, but if it doesn't work then do not push it too much neither, just stick to what they already have.