It would be helpful to hear why you think making Alda a more central character than Taz. Once I know this, I can give you another great steaming load of opinions.
Regarding Ch. 9 and your comment about Alda becoming the MC instead of Taz. Because the Chap. is all about Taz, I assume you mean to give Alda a bigger part in the series and reduce Taz's role altogether. This would take some work on your part, and I'm not sure the effort would improve anything.
Taz and Alda's characters do not compete for the relationship with Jay. Certainly they both know her, but from far different POVs. Taz and Alda are irreverent folks, and that makes them a good pair, or team. Taz being a non-believer, whilst Alda is a believer, and seems to accept her spiritual gifts grudgingly as more of a burden however, she complies out of a sense of duty to Jay as well as Behira.
I think both provide a good balance, and they appeal to Jay in their own special way. Being a member of the Wolves is special to Jay, and also provides a good anchor to previous books. I think diminishing Taz's role would be a mistake. That's not to say you can't amp up Alda's character or role. Because of Alda's sardonic view on almost everything she provides humor, however, too much 'may' make readers tire of her and Alda ends up being more glib than funny. I think you have a good balance with the triad of Jay, Taz, and Alda.