A pastoral need might dictate adult initiation take place at a time other than the Easter Vigil, but that would involve a reordering of the entire community’s focus. Here’s section 8:
8. The whole initiation must bear a markedly paschal character, since the initiation of Christians is the first sacramental sharing in Christ’s dying the rising and since, in addition, the period of purification and enlightenment ordinarily coincides with Lent (Sacrosanctum Concilium 109) and the period of postbaptismal catechesis or mystagogy with the Easter season. All the resources of Lent should be brought to bear as a more intense preparation of the elect and the Easter vigil should be regarded as the proper time for the sacraments of initiation. Because of pastoral needs however, the sacraments of initiation may be celebrated at other times (see nos. 26-30).
The paschal character of initiation should be obvious, but a Christ-centered baptism-confirmation-Eucharist must still buck the preconciliar attitudes of pelagianism and priest-centered instruction.
Note that teaching that “all the resources of Lent” should be utilized for the intensity of the final period for the elect. What would that mean? I would think an entire community fasting, praying, giving alms, not to mention the liturgical and devotional life of a parish. One hard-nosed theologian once said that sure, we can adapt an adult initiation to a period outside of Lent … if the whole parish wanted to commit to living a second Lent at another time of the year. But let’s keep perspective: the reforms in adult baptism were not intended to subject everything evangelical and catechetical in a parish to the pattern of liturgy, but rather to the ordering of initiation to Jesus Christ. The Church’s liturgy orders itself to Christ and his Paschal Mystery every year. That is the important time for adult initiation, not because it’s Lent, Easter Vigil, and Easter season, but because the mystery of Christ is at the core. And like initiation, the liturgy itself aligns with the mystery of Christ.