Two forms of the “funeral liturgy” are possible:
46. The section entitled “Funeral Liturgy” provides two forms of the funeral liturgy, the central celebration of the Christian community for the deceased: “Funeral Mass” and Funeral Liturgy outside Mass.” When one of its members dies, the Church especially encourages the celebration of the Mass. When Mass cannot be celebrated (see OCF 178), the second form of the funeral liturgy may be used and a Mass for the deceased should be celebrated, if possible, at a later time.
My sense of this instruction is that there be more than a Mass intention at a later time.
As for the three instances when a funeral Mass cannot be celebrated, you know they are (1) liturgical (another observance takes priority) or (2) when a priest is unavailable, or (3) when pastor and family judge a Mass is less suitable.