Extempore Eucharistic Prayers

Geoffrey Wainwright tells us that:

According to Justin Martyr (c. 150) the liturgical president extemporized the great eucharistic prayer (hose dunamis autoi, 1 Apol. 67), but various North African councils around AD 400 document the fact that the later moves towards complete fixity were due in part to the need to ensure the doctrinal orthodoxy of new prayers even when written down.... The Apostolic Tradition Of Hippolytus proposes prayers as ‘models’.

‘The Language of Worship’ pp519-528 in Jones, Wainwright, Yarnold, Bradshaw (ed.s) The Study of Liturgy revised edition (London, SPCK, 1992) pp526

Evangelicals have always seen the Word as essential to the sacraments, but I'm not quite sure what words need to be or ought to be included in the celebration of the Lord's Supper. I reckon something along the lines of 1 Corinthians 11:23-26 would be an irreducible minimum and that it would be good to have some kind of fencing of the table (see the following verses) and a sermon.

The eucharistic meditations at Edible Words seem like a good attempt to me to enrich our understandings of what we are doing in the supper. The Eucharistic Prayers in Common Worship don't seem like the be all and end all to me.