This person takes a completely different approach to the question - who are the 2 witnesses:

The Two Olive Trees and Two Witnesses, however, seem to be representative of the pure, invisible Church as seen from heaven. Here the invisible, Spirit-filled Church is reduced to its most vital component of Witness to the Christ - its most vital function upon earth! So the Olive Trees are the Two Witnesses, first foreshadowed by the ministries of Elijah and Elisha and then initially realized under the New Covenant by John the Baptist and Jesus, but now continuing to be realized wherever Christians preach the gospel! So, in a real sense, we are all part of the mission of the Two Witnesses! It should be seen at once that this is a wholly biblical approach which does not cut Revelation loose from the rest of God's Word - which should not happen.

Once we can see that Revelation 11 is set in the age of the Church's worldwide mission, we can see that we do not necessarily need to posit any future specific individuals yet to arrive on the world scene. As specific individuals, John the Baptist and Jesus have already come and gone, yet those of us who go out and witness with the gospel continue to wear their mantle, continuing the witness of the Church - Luke 10: 1-2, Acts 1: 8. A few commentators agree that Revelation needs to be 'earthed' on the rest of God's Word and uphold the principle for a while, but then appear to suddenly cast aside the principle, indulging in all kinds of flights of fancy! But we should be cautious! This is the inspired Word of God which must be treated with respect - read the warning of Revelation 22: 18-19!...

[link to www.ukapologetics.net]