I think a lot of this is just fanciful reconstruction/byzantinization.
Bishop Maelruain (Dowling) of the Celtic Orthodox Church has this to say on a
list devoted to Celtic Christianity.
They have added a form of epiclesis into the 8th century Lorrha Missal:
"The prayer we have chosen to use at every celebration of the Eucharist
is the Post Mysterium of the Feast of the Throne of Saint Peter, The
Post Mysterium is a variable proper to the feast day. Some feasts
have none and the P.M.s for those that do may or may not make
reference to the Bread and Wine becoming the Body and Blood.
"The primary reason we made this alteration in practice is that one
member of our synod felt strongly that the Byzantines needed it to
recognize the Eucharist as properly confected. Personally, I feel
that there are plenty of prayers throughout the Liturgy which serve
the same purpose, so I would not consider the Liturgy lacking without
the added specific epiklesis any more than I would consider the
Chrysostom Liturgy lacking because it lacks those other prayers.
"Some have tried to force me to use the Byzantine prayer, but I see no
value in doing so. "
Here is the prayer which Bishop Maelruain has added into the Lorrha Missal to
act as an epiclesis. It is the Post Mysterium prayer for the Feast of the
Throne of Saint Peter at Rome and it may be the origin of the Byzantine and
Mozarabic forms:"We who serve, offer these prescribed Holy Gifts of our Salvation, that Thou may
be pleased to send Thy Holy Spirit upon this Sacrifice so that it may be changed
into a legitimate Eucharist for us in the Name of Thee, Thy Son and the Holy
Spirit, in the transformation of the Body and Blood of our Lord Jesus Christ;
and may it be unto us who eat and drink, Life eternal and the eternal Kingdom.
Through Christ Himself Our Lord who reigneth with Thee and the Holy Spirit
throughout all ages of ages. Amen."