The depth of the squad can be something important for Ten Hag because next season they will play as one of the title contenders and if the current transfer market is not utilized well, it will be difficult to compete with Bayern Munich who are currently growing. For the Champions League, I do not favor Leverkusen next season because there are many things that make them look not so favorites. Ten Hag certainly deserves a chance but don't expect too much in terms of titles because the new manager will definitely need to adjust to the pace of competition in the League.
Let alone favoring Leverkusen in the Champions League next season, in the Bundesliga alone I am not sure to favor Leverkusen as a title contender if the coach is Ten Hag. Because next season, apart from Bayern Munich who will remain strong to be a title contender again, there is also Dortmund which can also be better because this has been seen immediately when Dortmund replaced their coach from Nuri Sahin to Niko Kovac. So Leverkusen might find it a little more difficult to balance their performance with several other teams including the Munich and Dortmund teams next season.