You need to first have a starting eleven before you can even think of squad depth, but as it is now some important players is already leaving the team and when new ones come they at least will need little time to adapt to the new coach tactics. I don't think Bayern Leverkusen will be able to compete with the likes of Bayern Munich as they did this season and the last because of the change of manager. The stake at the club will be high now because of what Alonso has done.
We have seen excellent performances from Leverkusen in the last two seasons. This was possible because of Xabi Alonso. Xabi Alonso will not be with Leverkusen next season. There are many doubts whether the team will be able to do well with the help of the new coach. More importantly, several important players in the Leverkusen squad are also leaving the team.
Ten Hag is going to be the coach of Leverkusen next season. Ten Hag will be given a decent fund by the Leverkusen management to strengthen the squad. So ten hag should spend money very carefully. Personally, I do not trust ten hag. Manchester United management spent a lot of money to buy players because of ten hag's shortsightedness. But the expected success is not seen.