A theologian once quipped that confirmation was a sacrament in search of a theology. Vatican II did make a few brief suggestions:
The rite of confirmation is to be revised and the intimate connection which this sacrament has with the whole of Christian initiation is to be more clearly set forth; for this reason it is fitting for candidates to renew their baptismal promises just before they are confirmed.
Confirmation may be given within the Mass when convenient; when it is given outside the Mass, the rite that is used should be introduced by a formula to be drawn up for this purpose.
Our previous bishop did celebrate confirmation outside of Mass. I had never experienced that before coming to Kansas City. I was not in favor of 40-minute homilies. They could easily have been trimmed in half to give the confirmandi and their families the opportunity to celebrate the Eucharist, as is always fitting.