h/t to the Shrine of the Holy Whapping
I'm assuming it would have the following plot:
The Priest is a hunchback who mentors the subdeacon, a seminarian, with a shady past and unknown origins. We discover all this by the Kyrie. The graduale is the hit chant "La Nonna Immobile" [in honor of a particularly ferociously stolid Italian churchlady, no doubt. --MGA] By the time we get to the Credo we learn that the subdeacon is actually the schola director in disguise, as the two happen to be identical twins. Confusion ensues, but is merrily resolved. At the Sanctus we discover that the priest and the deacon were switched at ordination (Two hunchbacks--Take that, Rigoletto!), and a fight breaks out at the first step (see Fortescue, p. 47 for the staging of said fight). By the Agnus Dei the deacon has killed the priest (thurible fight!), and repeats the prayer of consecration to make the Mass valid. While he says the prayers, the subdeacon and schola director join in in perfect counterpoint. The people receive communion and the Mass concludes with "Ah! Ah! La Benedictio-oh-ne!" The sacred ministers recess.
And it's all staged by Zeffirelli, with costumes by Wippel. Like the Mass will be in heaven.
Me, I think Mass in heaven has vestments by Vionnet, (who is surely there?)
A bias-cut chasuble, gothic or baroque, would just hang so beautifully...