I have just browsed through three erudite articles on 7th/8th century Roman practice and they are not too helpful!
Manifestly, the object which receives papal adoration in 8th century Santa Croce is simply a lump of wood upon which - literally - hung the Saviour of the world: a portion of the True Cross. (cf Egeria's account of the earlier practice in Jerusalem)
The documented practice of the presbyteral churches of Rome (7th century) speaks of a veneration of "the cross". Yet none of the authors I have skimmed through address the question of the possibility of "the cross" being a crucifix. Do they presume that it is or is it more likely to be a plain cross of wood? Personally, I am inclined towards the latter.
JA mentions that an icon would - as it were -
de facto cease to be without a figure. I'm not so sure. For example, our sensibilities towards the relics in Santa Croce today might be clouded by a tinge of incredulity - are these things authentic? (I myself found the cross-beam of the cross of the 'Good Thief' spiritually very moving but I confess to being a tiny bit quizzical about the bones of the finger of St Thomas which entered our Lord's side).
Yet might not a stout, plain piece of wood, a large nail (bent over at the point) and a copy of the INRI title be in itself iconic (i.e. - powerfully symbolic)? I might not want to kiss it but it would make me pause in silent contemplation for a moment and force me to utter (silently, perhaps) "We adore you O Christ, and we praise you....etc" Might not a reproduction of a nail used in crucifixion be as powerful on its own?
(
http://www.bgst.edu.sg/realia/nail.htm )
(By the way - we always use one large crucifix on Good Friday
)
Christ Pantocrator is replaced by Christ Crucified - iconography reflects spirituality and the upper basilica of San Clemente in Rome has (probably) the most famous mosaic of the crucifixion in the world. It's 11th century. (
http://www.basilicasanclemente.com/ )
I'll do a bit more research.........
A music question -
Who breaks up the reading of the Passion with hymns? (Don't say "The Lutherans". I know of one Catholic church that does this on Good Friday and I really don't know why it is done.)