Tell your priest he should check with his Bishop, I am guessing that his Bishop would tell him to either do it in its proper place during Great Compline of the Vigil, or after the Vesperal Liturgy or not to do it at all.
Yes, indeed. The hierarchs are particularly cautious with innovating during a great feast (as they should be). Definitely advise your priest to "clear" everything with the bishop first.
"O Cross of Christ, all-holy, thrice-blessed, and life-giving, instrument of the mystical rites of Zion, the holy Altar for the service of our Great Archpriest, the blessing - the weapon - the strength of priests, our pride, our consolation, the light in our hearts, our mind, and our steps"
Met. Meletios of Nikopolis & Preveza, from his ordination.