My opinion about Xabi Alonso is that he should stay at Bayer Leverkusen for 1 or 2 more seasons. Or he might become Erik Ten Hag. Erik Ten Hag is a very good small team/player manager. He can manage a small team with small players like Ajax very well. But when he came to Manchester United, he immediately started having problems with some of the big players in the team.
So it is very clear that he is not a big team manager. Xabi Alonso probably is also not ready to manage a team as big as Liverpool or Manchester United. The expectations are high, the media is ruthless over there. A relatively less experienced manager might struggle a lot there.
I don't think any requirement for Xabi Alonso staying one or two years later with Bayern Leverkusen if success win domestic league and Europe League this season, he was success with the second season become Bayern Leverkusen manager and most successful by stopping Bayern Munich dominance for winning domestic league. Its moment for Xabi Alonso moving the higher level of his manager position by accepting the top teams interested from Liverpool or Bayern Munich.
I think must be priority acceptable Liverpool's management interested and he will be in most difficult competition such as Premier League, its not easy such as Bundesliga with one compete teams but in Premier League all participants will be difficult and get difference result every week, I think not related when comparison between Erik ten Hag and Xabi Alonso reputation if accept with Liverpool interested.