OhMalley is saying: “Could your local bishop say that the purification will always take place during the Mass and not directly after it? Sure – that’s within his authority and it does not contravene the GIRM.”
I think this would be beyond is authority. The GIRM is clearly saying the purifications can be done after Mass.
From the 2002 General Instruction of the Roman Missal (GIRM) approved for the USA, which can be accessed from
romanrite.com/girm.html :
“163. … Nevertheless, it is also permitted, especially if there are several vessels to be purified, to
leave them suitably covered on a corporal, either at the altar or at the credence table, and to
purify them immediately after Mass following the dismissal of the people.”
“183. … It is also permissible to leave the vessels that need to be purified,
suitably covered, at the credence table on a corporal and to purify them immediately after Mass
following the dismissal of the people.”
(Plus the GIRM n. 279 I quoted in other posts above).
The GIRM has Chapter IX with the title “Adaptations Within the Competence of Bishops and Bishops’ Conferences”. There is has:
“387. The Diocesan Bishop, who is to be regarded as the high priest of his flock, and from
whom the life in Christ of the faithful under his care in a certain sense derives and upon whom it
depends,148 must promote, regulate, and be vigilant over the liturgical life in his diocese. It is to
him that in this Instruction is entrusted the regulating of the discipline of concelebration (cf.
above, nos. 202, 374) and the establishing of norms regarding the function of serving the priest at
the altar (cf. above, no. 107), the distribution of Holy Communion under both kinds (cf. above,
no. 283), and the construction and ordering of churches (cf. above, no. 291). With him lies
responsibility above all for fostering the spirit of the Sacred Liturgy in the priests, deacons, and
faithful.”
So there are specific things an individual bishop can decide and the time of the purifications is not one of them. The bishop cannot say (about something so explicitly permitted) that it is not permitted.