Is it permissible to pay the deferred dower (mu'akhkhar) of a wife (who is still married to her husband) in the form of gifts, by mutual agreement and consent of both spouses, such that the value of the gift is deducted from the total deferred dower?

There is no objection to settling a wife's deferred dower (mahr) with specific items, gifts, and the like, by mutual agreement and consent of both spouses. This is akin to selling these items to the wife in exchange for the dower owed by the husband, and it is permissible. If it is permissible for the wife to waive her dower, then it is even more permissible for her to receive specific items as compensation for all or part of the dower.