since you you are working with the same company, your sponsor first impression might be you are planning to terminate your wife contract with them and find better opportunities elsewhere. This is the reality. There is no good reason to change her sponsorship to you.

and for the record, ministry is giving a strict approval for Family Sponsorship in order to protect local companies and businesses around due to easily switching job. I heard a lot of application are rejected due to this reasons ministry incharge are carefully examining, checking, investigating applications.